[DOCS] Additional note in impala_alter_database
[DOCS] Additional note in impala_alter_database

- Added a note about the effective ALL with GRANT and ALL without
GRANT privileges.

Change-Id: Idf2cb58993adadb7fb32ec188f5e4dff216c5897
Reviewed-on: http://gerrit.cloudera.org:8080/11703
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>
Reviewed-by: Fredy Wijaya <a7b1ea89bd1075d63bc457238443aca86dd9cc1a@cloudera.com>

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