Remove IDENTIFIED BY clause for MySQL REVOKE

IDENTIFIED BY is not documented for REVOKE in MySQL 5.5 and 5.6 and
furthermore produces a syntax error on MySQL 5.6.

Change-Id: Ib7bf1ba0ce049c1ed8a90292064a1e05724170e0
Closes-Bug: #1292690
Merge "Remove IDENTIFIED BY clause for MySQL REVOKE"