RFR: Increase timeout for TestGCOldWithShenandoah

[Roman Kennke]

I ran into timeout problems with GCOld jtreg test on a big (but not
fast) aarch64 box. This was all in heap verification code
(single-threaded). Did some profiling, nothing obvious turned up, except
lots of cache misses that we can't fix. This patch ups the timeout for
the affected tests.

http://cr.openjdk.java.net/~rkennke/timeout/webrev.00/

Ok?