I was facing the same issue after installation of a fresh cluster. The Metastore server wouldn't start and hang at executing "yarn rmadmin -refreshSuperUserGroupsConfiguration"
The cause was that the master node on which the Hive MetaStore was installed, was not the same as the node where Yarn ResourceManager was located. Therefore Yarn client and yarn-site.xml were not automatically available for successfully connect to the ResourceManager on another host. By just adding Yarn Client to the host where Metastore Server was installed, the problem was resolved.
The reason why adding a second ResourceManager resolved the issue in @Guozhen Li's case, was probably because the second ResourceManager was installed on the same node where the Hive Metastore was located. Therefore addition of the Yarn client and the yarn-site.xml file remedied the problem.