[Flink] set parallelism to 1

Author: jto

gradle.properties

@@ -16,7 +16,7 @@
 # limitations under the License.
 ################################################################################
 org.gradle.caching=true
-org.gradle.parallel=false
+org.gradle.parallel=true
 org.gradle.daemon=false
 org.gradle.configureondemand=true
 org.gradle.jvmargs=-Xss10240k

runners/flink/flink_runner.gradle

@@ -271,7 +271,7 @@ def createValidatesRunnerTask(Map m) {
       project(":runners:core-java").sourceSets.test.output.classesDirs,
     )
     // maxParallelForks decreased from 4 in order to avoid OOM errors
-    maxParallelForks 2
+    maxParallelForks 1
     def flinkConfDir = System.getProperty("user.dir") + "/runners/flink/src/test/validatesRunnerConfig"
     environment("FLINK_CONF_DIR", flinkConfDir)
     useJUnit {