Automatic merge from submit-queue (batch tested with PRs 50692, 50727)
remove leaked socket file after unit test
Before this change:
```
$ make test WHAT=k8s.io/kubernetes/pkg/master
+++ [0816 11:19:03] Running tests without code coverage
ok k8s.io/kubernetes/pkg/master 27.953s
$ find -type s
./pkg/master/127.0.0.1:2100324511
./pkg/master/127.0.0.1:2100424511
./pkg/master/localhost:8235197834378812860
./pkg/master/localhost:82351978343788128600
./pkg/master/127.0.0.1:2100524511
./pkg/master/127.0.0.1:2100624511
./pkg/master/localhost:1155389051645284688
./pkg/master/localhost:11553890516452846880
```
**Release note**:
```
NONE
```
02ad43917c