public boolean shouldLoginFromKeytab() {
    return User.shouldLoginFromKeytab(this.getConf());
  }
In secure environment, if a user specified his keytab and principal, a hbase client will try to
login with them. Otherwise, hbase client will try to obtain ticket(through kinit) from system.
hbase-common/src/main/java/org/apache/hadoop/hbase/security/UserProvider.java