gdb: Run INF_EXEC_COMPLETE handler for additional cases

gdb: Run INF_EXEC_COMPLETE handler for additional cases

When making an inferior call, and non-stop mode is off, then, once the
inferior call is complete all threads will be stopped, and we should
run the INF_EXEC_COMPLETE handler.  This will result in a call to
'target_async(0)' to remove the event handlers for the target.

This was discussed by Yao Qi in this mailing list thread:

    https://sourceware.org/ml/gdb/2017-10/msg00032.html

Without this then the target event handlers are left in place even
when the target is stopped, which is different to what happens during
a standard stop proceedure (for example when one thread hits a
breakpoint).

gdb/ChangeLog:

	PR gdb/22882
	* infrun.c (fetch_inferior_event): If GDB is not proceeding then
	run INF_EXEC_COMPLETE handler, even when not calling normal_stop.
	Move should_notify_stop local into more inner scope.