Use python2 in Python script shebang lines

This fixes issue #3336.

poller-service.py

@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python2
 """
  poller-service A service to wrap SNMP polling.  It will poll up to $threads devices at a time, and will not re-poll
                 devices that have been polled within the last $poll_frequency seconds. It will prioritize devices based