public static void login(String keytabLocation, String principalName) throws IOException {
      if (isSecurityEnabled()) {
        UserGroupInformation.loginUserFromKeytab(principalName, keytabLocation);
      }
    }
Login through configured keytab and pricipal.
@param keytabLocation location of keytab
@param principalName  principal in keytab
@throws IOException exception from UserGroupInformation.loginUserFromKeytab
hbase-common/src/main/java/org/apache/hadoop/hbase/security/User.java