Mark the "step over single instruction" plan private in the StopInfoWatchpoint::PerformAction to
ensure that the watchpoint not the step is reported as the stop reason.  Also, stash away & restore
the current stop reason just so it can't go away on us.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@185474 91177308-0d34-0410-b5e6-96231b3b80d8