gc/logging/TestMetaSpaceLog.java doesn't work for ZGC

The test gc/logging/TestMetaSpaceLog.java is disabled (after JDK-8212630) for ZGC because it would fail if run.

I think it's partially a ZGC bug that it doesn't work. The test expects to find the output from a call to print_metaspace_chage(), but ZGC never calls that function. (Unless it's intentional that ZGC doesn't call that function and can't pass this test.)

The test also seems to be wrong; it expects "[gc,metaspace" info log messages only of the form produced by print_metaspace_change, but ZGC has ZStatMetaspace::print(), which produces a log message not expected by the test.