Minor changes and improvements.
*Changing mutable default args in rpc_api to None
*py26 changes

Change-Id: Iabc34971666d0bfe9e0875f5764146fc31681e84
Merge remote-tracking branch 'cisco/csr1kv_for_routing_juno' into csr1kv_for_routing_juno
Merge remote-tracking branch 'cisco/csr1kv_for_routing_juno' into csr1kv_for_routing_juno