Refactor caching in poolmgr

Move separate caches to one cache -- functionServiceCache.  It can be
looked up by function, can update atime by address, and can be deleted
by podname.  This removes the other caches.  Some of the concurrency
logic is still a bit hairy; it might be better not to use fission.Cache.

poolmgr/functionServiceCache_test.go

@@ -0,0 +1,72 @@
+package poolmgr
+
+import (
+	"log"
+	"testing"
+
+	"github.com/platform9/fission"
+	"time"
+)
+
+func TestFunctionServiceCache(t *testing.T) {
+	fsc := MakeFunctionServiceCache()
+	if fsc == nil {
+		log.Panicf("error creating cache")
+	}
+
+	var fsvc *funcSvc
+	now := time.Now()
+
+	fsvc = &funcSvc{
+		function: &fission.Metadata{
+			Name: "foo",
+			Uid:  "1212",
+		},
+		environment: &fission.Environment{
+			Metadata: fission.Metadata{
+				Name: "foo-env",
+				Uid:  "2323",
+			},
+			RunContainerImageUrl: "fission/foo-env",
+		},
+		address: "xxx",
+		podName: "yyy",
+		ctime:   now,
+		atime:   now,
+	}
+	err, _ := fsc.Add(*fsvc)
+	if err != nil {
+		fsc.Log()
+		log.Panicf("Failed to add fsvc: %v", err)
+	}
+
+	f, err := fsc.GetByFunction(fsvc.function)
+	if err != nil {
+		fsc.Log()
+		log.Panicf("Failed to get fsvc: %v", err)
+	}
+	fsvc.atime = f.atime
+	fsvc.ctime = f.ctime
+	if *f != *fsvc {
+		fsc.Log()
+		log.Panicf("Incorrect fsvc \n(expected: %#v)\n (found: %#v)", fsvc, f)
+	}
+
+	err = fsc.TouchByAddress(fsvc.address)
+	if err != nil {
+		fsc.Log()
+		log.Panicf("Failed to touch fsvc: %v", err)
+	}
+
+	err = fsc.DeleteByPod(fsvc.podName)
+	if err != nil {
+		fsc.Log()
+		log.Panicf("Failed to delete fsvc: %v", err)
+	}
+
+	_, err = fsc.GetByFunction(fsvc.function)
+	if err == nil {
+		fsc.Log()
+		log.Panicf("found fsvc while expecting empty cache", err)
+	}
+}