Fix deadlock in VirtualMachine.AllThreads

We cannot add any object in the JDWP object registry while holding the
Locks::thread_list_lock. Indeed we may need to suspend a thread and take it,
causing a deadlock by waiting for ourself on this lock.

Bug: 17343664
Change-Id: I2335c63e418c0d485daf2c35f8debcd52f943140
2 files changed