Reap idle pods

Idle pod reaper wakes up once a minute, looks in the functionServiceCache for pods that
haven't been accessed for more than idlePodReapTime, and deletes all such pods.

(This doesn't yet delete pods that may be leaked from previously terminated poolmgrs; it
only works with pods created by the current poolmgr instance.)

poolmgr/api.go

@@ -127,8 +127,6 @@ func (api *API) getServiceForFunction(m *fission.Metadata) (string, error) {
 		return fsvc.address, nil
 	}
 
-	api.fsCache.Log()
-
 	// None exists, so create a new funcSvc:
 	log.Printf("[%v] No cached function service found, creating one", m.Name)