IMPALA-5514: Throw an error when --ldap_password_cmd is used without LDAP auth
IMPALA-5514: Throw an error when --ldap_password_cmd is used without LDAP auth

When only with ldap_password_cmd option, impala-shell runs successfully.

I solved this problem by throwing an error when --ldap_password_cmd is
used without LDAP auth, that is, ldap_password_cmd option will only
take effect if ldap option presents.

Change-Id: I3711d8a0eca2fa8612e2943fa9121945db6b012e
Reviewed-on: http://gerrit.cloudera.org:8080/7188
Reviewed-by: Bharath Vissapragada <f23dbca75acdac4082d6a05c290fc03565dada86@cloudera.com>
Tested-by: Impala Public Jenkins

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala