Relax open file descriptor assertion in stress test

Allow number of open file descriptors to grow at most 50% instead
of 30%. Lower value results in this test build flaky when executed
as part of the build. Long running dedicated build shows no
indications of leaks as well as local runs.

Author: lutovich

driver/src/test/java/org/neo4j/driver/v1/stress/AbstractStressTestBase.java

@@ -307,8 +307,8 @@ private void assertNoFileDescriptorLeak( long previousOpenFileDescriptors )
     {
         System.out.println( "Initially open file descriptors: " + previousOpenFileDescriptors );
 
-        // number of open file descriptors should not go up for more than 30%
-        long maxOpenFileDescriptors = (long) (previousOpenFileDescriptors * 1.3);
+        // number of open file descriptors should not go up for more than 50%
+        long maxOpenFileDescriptors = (long) (previousOpenFileDescriptors * 1.5);
         long currentOpenFileDescriptorCount = getOpenFileDescriptorCount();
         System.out.println( "Currently open file descriptors: " + currentOpenFileDescriptorCount );