Gremlin Server Krb5Authenticator is for authenticating gremlin clients towards Gremlin Server. Apparently, you do not want it, so remove it from your configs.
Apparently you are trying to have Gremlin Server authenticate againts HBase. This has nothing to do with Gremlin Server's Krb5Authenticate. If the keytab for Gremlin Server is OK and a kinit was done on the Gremlin Server host with the right user, the hbase client of janusgraph-hbase, running on the Gremlin Server host, should be able to access the TGT and authenticate to HBase.
