Get debugserver to call task_set_state to prime the control registers so that watchpoints
take for threads created while the program is running.  Remove the testcase skips from TestConcurrentEvents.py,
since they all pass now, and fix TestWatchpointMultipleThreads.py - which should have caught this problem -
so it doesn't artificially break on new thread creation before the watchpoint triggers.

llvm.org/pr16566
<rdar://problem/14383244>