always restart mysql service when my.cnf changes

In upstream mysql coobkook, changes to the my.cnf template will only
trigger a reaload, not a restart.  This patch forces a restart on
changes to the template, so that things like changing bind_ip actually get
effected properly.

Workaround for upstream bug  https://tickets.opscode.com/browse/COOK-4161
Fixes: https://github.com/rcbops/chef-cookbooks/issues/910

(cherry picked from commit 311d66f7d1dacf9887fe322cf272e11726751869)