Remove conflicting GC options from test command line

Some tests requires specific GC flags. When extra GC options are added by the test framework, then the test wiill fail.

Function removeGcOpts() in testlibrary/jdk/testlibrary/Utils.java is used to remove extra GC options from the command line. That function currently removes all options with pattern "-XX:+-Use*GC". It should also remove the following options:
-Xconcgc
-Xincgc