Description of problem:
Fail to get Metrics, and can not auto scale

Version-Release number of selected component (if applicable):
3.7.0


Steps to Reproduce:
1: oc new-project sszr1 
2: oc create -f https://raw.githubusercontent.com/openshift-qe/v3-testfiles/master/hpa/rc-hello-openshift.yaml
3: oc autoscale rc/hello-openshift --min=2 --max=10
4: oc get hpa

The actual result:
NAME              REFERENCE                               TARGETS           MINPODS   MAXPODS   REPLICAS   AGE
hello-openshift   ReplicationController/hello-openshift   <unknown> / 80%   2         10        0          1m

The expected result: the target value should be some digital value, not "unknown" 

5: if check the number of pod "oc describe replicationcontrollers hello-openshift", will show only 1 pod, the expected value should be at least 2.

Addition info: found the following log in master:
 Oct  9 06:15:25 ip-172-18-10-208 atomic-openshift-master-controllers: E1009 10:15:25.022268   13121 horizontal.go:206] failed to query scale subresource for ReplicationController/dma/hello-openshift: User "system:serviceaccount:openshift-infra:horizontal-pod-autoscaler" cannot get replicationcontrollers.extensions/scale in the namespace "dma": User "system:serviceaccount:openshift-infra:horizontal-pod-a
<deshuai> <deshuai> utoscaler" cannot get replicationcontrollers/scale.extensions in project "dma" (get replicationcontrollers.extensions hello-openshift)