Ignore errors prefetching database_grant

If database_grant couldn't be prefetched because there was no /root/.my.cnf
this error can be ignored becuase it is tried again when its needed. So packstack
can ignore this error from the puppet apply
https://bugzilla.redhat.com/show_bug.cgi?id=904671

Change-Id: I365757ce70a798c209833aa8f3dbc596c8a9d8c2