Automatic merge from submit-queue

genericapiserver: Moving InstallSwaggerAPI to Run

Ref https://github.com/kubernetes/kubernetes/pull/21190#discussion_r57494673

Moving InstallSwaggerAPI() from InstallAPIGroups() to Run(). This allows the use of InstallAPIGroups() multiple times or using InstallAPIGroup() directly.

cc @jianhuiz @kubernetes/sig-api-machinery