check grants in mysql plugins

[Andrew Garner]

The various mysql plugins should check grants and verify that we have the correct privileges. This allows us to fail early and with a more clear error message and avoid some nasty silent MySQL behaviors. For instance if we lack the TRIGGER privilege, triggers will silently be skipped by mysqldump and the backup will be missing data.

mysqldump effectively needs (for 5.1+):

SELECT, SHOW VIEW, RELOAD, SUPER, LOCK TABLES, REPLICATION CLIENT, EVENT, TRIGGER

(SUPER is required for stop-slave)

mysql-lvm needs:

RELOAD, REPLICATION CLIENT

But mysqldump-lvm will have the same requirements as mysqldump

xtrabackup is essentially the same:

RELOAD, REPLICATION CLIENT, SUPER

Ideally holland should also have a command for generating the right grant for the current mysql version.