Fix a deadlock between debugger and GC.

Avoid a deadlock between GC and debugger's SuspendAllForDebugger where
GC gets suspended during GC.

Fix the jdwp tests with the CC collector, but the deadlock is NOT
specific to the CC collector.

Bug: 25800335
Bug: 12687968
Change-Id: I8f2869872bce4692d943020072e35ebf5a4e68a5
4 files changed