strato concurrent tests

1. making strato related tests concurrent as they are timing out on CI at this point
2. adding syncronized to Hotspot snapshot method as it is not thread safe. in particular when we lookup GC name we call PerfStringCounter that calls super PerfByteArrayCounter that resets buffer position to 0. if called concurrently one thread will read the counter resetting position to buffer length and we get BufferUnderflow i.e. race condition
https://github.com/AdoptOpenJDK/openjdk-jdk11u/blob/master/src/java.management/share/classes/sun/management/counter/perf/PerfByteArrayCounter.java#L53
https://github.com/AdoptOpenJDK/openjdk-jdk11u/blob/master/src/java.management/share/classes/sun/management/counter/perf/PerfStringCounter.java#L64

Stack trace:
https://ton.pdxa.twitter.com/scoot/prod_d70f787a-276c-4db8-7e76-36016e1ef442_08fbec44-75f9-482d-7f87-b240c9af3c1e/stdlog

```
generated columnDescs match generated ops(com.twitter.strato.config.compile_tests.ColumnDescTest)
java.nio.BufferUnderflowException
	at java.base/java.nio.DirectByteBuffer.get(DirectByteBuffer.java:294)
	at java.base/java.nio.ByteBuffer.get(ByteBuffer.java:770)
	at java.management/sun.management.counter.perf.PerfByteArrayCounter.byteArrayValue(PerfByteArrayCounter.java:57)
	at java.management/sun.management.counter.perf.PerfStringCounter.stringValue(PerfStringCounter.java:64)
	at java.management/sun.management.counter.perf.PerfStringCounter.getValue(PerfStringCounter.java:58)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at com.twitter.jvm.Hotspot.$anonfun$getGc$5(Hotspot.scala:90)
	at scala.Option.map(Option.scala:230)
	at com.twitter.jvm.Hotspot.$anonfun$getGc$4(Hotspot.scala:90)
	at com.twitter.jvm.Hotspot.$anonfun$getGc$4$adapted(Hotspot.scala:89)
	at scala.Option.flatMap(Option.scala:271)
	at com.twitter.jvm.Hotspot.$anonfun$getGc$2(Hotspot.scala:89)
	at com.twitter.jvm.Hotspot.$anonfun$getGc$2$adapted(Hotspot.scala:88)
	at scala.Option.flatMap(Option.scala:271)
	at com.twitter.jvm.Hotspot.getGc(Hotspot.scala:88)
	at com.twitter.jvm.Hotspot.snap(Hotspot.scala:149)
	at com.twitter.strato.config.loading.ConfigResourceMonitoring$.collect(ConfigResourceMonitoring.scala:55)
	at com.twitter.strato.config.loading.CompiledStratoCatalog.<init>(CompiledStratoCatalog.scala:56)
	at com.twitter.strato.config.loading.CompiledStratoCatalog$.apply(CompiledStratoCatalog.scala:493)
	at com.twitter.strato.test.config.ConfigTestCatalog$$anon$1.mkConfigCatalog(ConfigTestCatalog.scala:333)
	at com.twitter.strato.test.config.ConfigTestCatalog$.apply(ConfigTestCatalog.scala:159)
	at com.twitter.strato.test.config.StratoConfigSuite.mkCatalog(StratoConfigSuite.scala:164)
	at com.twitter.strato.config.compile_tests.ColumnDescTest.$anonfun$new$1(ColumnDescTest.scala:18)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
	at com.twitter.servo.testing.prop.PropertySuite.$anonfun$test$1(PropertySuite.scala:71)
```

Differential Revision: https://phabricator.twitter.biz/D1188541

Author: Evgenii Slutckii

util-jvm/src/main/scala/com/twitter/jvm/Hotspot.scala

@@ -4,15 +4,15 @@ import com.twitter.conversions.StorageUnitOps._
 import com.twitter.conversions.DurationOps._
 import com.twitter.util.Time
 import java.lang.management.ManagementFactory
-import java.util.logging.{Level, Logger}
-import javax.management.openmbean.{CompositeData, CompositeDataSupport}
-import javax.management.{
-  Notification,
-  NotificationEmitter,
-  NotificationListener,
-  ObjectName,
-  RuntimeMBeanException
-}
+import java.util.logging.Level
+import java.util.logging.Logger
+import javax.management.openmbean.CompositeData
+import javax.management.openmbean.CompositeDataSupport
+import javax.management.Notification
+import javax.management.NotificationEmitter
+import javax.management.NotificationListener
+import javax.management.ObjectName
+import javax.management.RuntimeMBeanException
 import javax.naming.OperationNotSupportedException
 import scala.jdk.CollectionConverters._
 import scala.language.reflectiveCalls
@@ -115,7 +115,7 @@ class Hotspot extends Jvm {
     }
   }
 
-  def snap: Snapshot = {
+  def snap: Snapshot = synchronized {
     val cs = counters("")
     val heap = for {
       invocations <- cs.get("sun.gc.collector.0.invocations").map(long)