Remove quit hook in CMIDriver::DoMainLoop (MI)

Summary:
This patch removes quit hook and fixes 1 bug:
# Fix "quit" hook in CMIDriver::DoMainLoop (MI)
# Fix bug when the handler thread exits without any notification (MI)
# Fix a race condition in CMICmnLLDBDebugger::MonitorSBListenerEvents (MI)

Test Plan: ./dotest.py -v --executable $BUILDDIR/bin/lldb tools/lldb-mi/

Reviewers: abidh

Reviewed By: abidh

Subscribers: lldb-commits, abidh

Differential Revision: http://reviews.llvm.org/D9275

llvm-svn: 236702