Removed dependency on mon[0]

Instead of using mon[0]'s hostname during fetch and mon[0]'s ansible_fqdn during OSD, MDS, RGW installation, we now use FSID instead. This solves an issue where fetch and ansible_fqdn sometimes won't match and OSD, MDS, RGW provisioning will fail. 

Also, since we're now using FSID, we can run the fetch command on all [mons] hosts. This removes our dependency on mon[0]. Fetch will now copy from the first "reachable" host and will just skip the rest.