qemurunner: Handle qemu start failure correctly

If qemu didn't start correctly, we may not have registered the child
signal. This results in a nasty traceback which confuses the underlying
issue. Cleanup this code and make the handler cleanup conditional.

(From OE-Core rev: 0ead936925c61aaaa7a819f6c5b999ba3a4daeda)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/qemurunner.py

@@ -258,8 +258,9 @@ class QemuRunner:
 
     def stop(self):
         self.stop_thread()
-        if self.runqemu:
+        if hasattr(self, "origchldhandler"):
             signal.signal(signal.SIGCHLD, self.origchldhandler)
+        if self.runqemu:
             os.kill(self.monitorpid, signal.SIGKILL)
             logger.info("Sending SIGTERM to runqemu")
             try:
@@ -279,7 +280,6 @@ class QemuRunner:
             self.server_socket = None
         self.qemupid = None
         self.ip = None
-        signal.signal(signal.SIGCHLD, self.origchldhandler)
 
     def stop_thread(self):
         if self.thread and self.thread.is_alive():