prefect unit test cases for annotation.proxy

[chentao1596]

1. prefect unit test cases for annotation.proxy;
2. for the line 91 & 95, i think "Fatalf" will be better than "Errorf", because if error occurs, the next process will no need to execute.
   thank you!

[k8s-reviewable]

This change is 

[coveralls]

Coverage increased (+0.2%) to 43.213% when pulling a8d235c8139b9611d17f4435ea74b4891b5be079 on chentao1596:proxy-main-test into 527159e on kubernetes:master.

[coveralls]

Coverage increased (+0.1%) to 43.152% when pulling 5990359 on chentao1596:proxy-main-test into 527159e on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@chentao1596 thanks!