runqueue.py: initialize rqexe at RunQueue's init function

Sometimes user stops the build before runqueue is established,
for example, at the stage of running add_unresolved() function. This
will cause RunQueue to use rqexe field in finish_runqeue() before
initialized. This will cause endless print of "Running idle function"
if use process server.

This commit initialize rqexe variable in RunQueue's init function,
and add a judgement in finish_runqueue().

(Bitbake rev: 59f817723172092a87738c79f555e605f55ea375)

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -779,6 +779,8 @@ class RunQueue:
         # For disk space monitor
         self.dm = monitordisk.diskMonitor(cfgData)
 
+        self.rqexe = None
+
     def check_stamps(self):
         unchecked = {}
         current = []
@@ -996,6 +998,9 @@ class RunQueue:
         return retval
 
     def finish_runqueue(self, now = False):
+        if not self.rqexe:
+            return
+
         if now:
             self.rqexe.finish_now()
         else: