Change roles to role when searching for ceph-mon

roles searches the expanded run list. This isn't
available for other nodes to search until the
run completes. This means you must run chef on
one mon at a time and your initial mons can only
be one mon. If more than one mon is used the
chef run get stuck trying to get the bootstrap
osd keyring.
Merge pull request #67 from git-harry/master

Change roles to role when searching for ceph-mon