RFR (S): 8164660: MinimalVM is not tested with GC tests

[Dmitry Fazunenko]

Hello,

I'm looking for reviewers for a simple change  needed for better 
selection of tests applicable for minimal VM.
There are two sort of changes:
- removing '@modules java.management' (if it's not needed)
- adding @requires vm.gc.X  (to those tests which ignore external flags 
and keep passing even if conflicting collector is given)

https://bugs.openjdk.java.net/browse/JDK-8164660
http://cr.openjdk.java.net/~dfazunen/8164660/webrev.00/

Thanks
Dima