Don't use := when some vars are defined

:= attempts to declare as many of the variables on its left side as it
can, instead of re-using as many as it can.  Consider this code:

   a, ok := foo()
   if !ok {
      a, err := bar()
      ...
   }

The inner 'a' is a different var from the outer one, and goes out of
scope at the }.  The outer 'a' is left with whatever value foo()
returned.

poolmgr/gpm.go

@@ -56,9 +56,10 @@ func (gpm *GenericPoolManager) service() {
 	for {
 		select {
 		case req := <-gpm.requestChannel:
+			var err error
 			pool, ok := gpm.pools[*req.env]
 			if !ok {
-				pool, err := MakeGenericPool(gpm.controllerUrl, gpm.kubernetesClient, req.env, 3, gpm.namespace)
+				pool, err = MakeGenericPool(gpm.controllerUrl, gpm.kubernetesClient, req.env, 3, gpm.namespace)
 				if err != nil {
 					req.responseChannel <- &response{error: err}
 					continue