Clean up the locks around Heap::VisitObjects().

This is so that we could support suspending all threads when visiting
objects in the presence of a concurrent, moving collector.

Bug: 12687968
Change-Id: Icc8e60630465afde948ebc6ea91d4ebaff5d7837
diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index c595de7..c63e2d7 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -2194,6 +2194,7 @@
     case kWaitingForJniOnLoad:
     case kWaitingForMethodTracingStart:
     case kWaitingForSignalCatcherOutput:
+    case kWaitingForVisitObjects:
     case kWaitingInMainDebuggerLoop:
     case kWaitingInMainSignalCatcherLoop:
     case kWaitingPerformingGc: