Check that RestartedFromEvent flag before processing the state changed event.

Not checking for this flags caused lldb-mi to issue stop notification when target
has started running again. It also tried to get stack when target was running and
this caused randon failure.

Approved in http://lists.cs.uiuc.edu/pipermail/lldb-dev/2015-March/006953.html

llvm-svn: 232370