database/sql: fix clean-mysql-binlog notify

In 2.2 release of puppetlabs-mysql, we have to notify the service mysqld
itself instead of using an old exec.
database/sql: fix clean-mysql-binlog notify

table, user and privilegs args of mysql_grant are required arguments
in 2.2 release of puppetlabs-mysql.

This commit remove alos the require on my.cnf and mysqld (this cause a
cycle dependency)
Merge pull request #563 from enovance/mysql-2.2

Fix MySQL service with PL-2.2