cgroup MetricsTester testMemorySubsystem fails sometimes when testing memory.kmem.tcp.usage_in_bytes

The testMemorySubsystem test in MetricsTester.java sometimes fails with messages like this :

java.lang.RuntimeException: Test failed for - memory:memory.kmem.tcp.usage_in_bytes, expected [655360], got [786432]
at jdk.test.lib.containers.cgroup.MetricsTester.fail(MetricsTester.java:207)
at jdk.test.lib.containers.cgroup.MetricsTester.testMemorySubsystem(MetricsTester.java:309)

I looked into the checking code, and looks like there is an error margin allowed in CgroupMetricsTester, which is currently 0.1 .
This might be changed to a somewhat higher value, e.g. 0.25 to make the test more robust.