Collect sensors from all Mibs

Previously the code would stop after finding sensors from one of the
Mibs gotten from self.mibfactory().
Now it goes through all the mibs and stores sensors from all of them

This makes it possible to get JuniperDomMib sensors and JuniperMib temperature data
but does it break other stuff?

python/nav/ipdevpoll/plugins/sensors.py

@@ -77,7 +77,6 @@ def handle(self):
                     "Found %d sensors from %s", len(all_sensors), type(mib).__name__
                 )
                 self._store_sensors(all_sensors)
-                break
 
     @defer.inlineCallbacks
     def mibfactory(self):