[8u60] Request for approval for 8050825 - Support running regression tests using jtreg_tests+TESTDIRS from top level

[David Holmes]

Please approve this backport to 8u60, the patch from 9 applied cleanly.

Bug: https://bugs.openjdk.java.net/browse/JDK-8050825
JDK 9 changeset: http://hg.openjdk.java.net/jdk9/jdk9/rev/de68e6f9139a
Original review thread: 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-July/027791.html

Thanks,
David