Removing AppEngine restriction on Java version. (#1944)

* Updating AppEngine Java version.

* update

Author: Vizerai

impl_core/src/main/java/io/opencensus/implcore/internal/DaemonThreadFactory.java

@@ -22,11 +22,6 @@
 
 /** A {@link ThreadFactory} implementation that starts all {@link Thread} as daemons. */
 public final class DaemonThreadFactory implements ThreadFactory {
-  // AppEngine runtimes have constraints on threading and socket handling
-  // that need to be accommodated.
-  public static final boolean IS_RESTRICTED_APPENGINE =
-      System.getProperty("com.google.appengine.runtime.environment") != null
-          && "1.7".equals(System.getProperty("java.specification.version"));
   private static final String DELIMITER = "-";
   private static final ThreadFactory threadFactory = MoreExecutors.platformThreadFactory();
   private final AtomicInteger threadIdGen = new AtomicInteger();
@@ -44,9 +39,12 @@ public DaemonThreadFactory(String threadPrefix) {
   @Override
   public Thread newThread(Runnable r) {
     Thread thread = threadFactory.newThread(r);
-    if (!IS_RESTRICTED_APPENGINE) {
+    // AppEngine runtimes have constraints on thread renaming.
+    try {
       thread.setName(threadPrefix + threadIdGen.getAndIncrement());
       thread.setDaemon(true);
+    } catch (SecurityException e) {
+      // OK if we can't set the name or daemon in this environment.
     }
     return thread;
   }