RFR: 8023491: (xs) Remove target names from root repo test/Makefile and defer to sub-repo makefiles

[Mike Duigou]

Hello all;

This review is for changes related to Alan's change JDK-8023351. This changeset removes knowledge of the test suites from the root repo test/Makefile and merely runs the sub-repo test/Makefile with the matching selection of targets. It also corrects issues with running the the langtools jtreg tests. Finally, the refined TEST variable is now passed to the sub-repo test/Makefiles in preparation for switching from using make targets to using TEST.groups

http://cr.openjdk.java.net/~mduigou/JDK-8023491/0/webrev/

Cheers,

Mike