If the Storage Pool Namespace XML data exists, format the mount
options on the MOUNT command line and issue a VIR_WARN to indicate
that the storage pool was tainted by custom mount_opts.

When the pool is started, the options will be generated on the
command line along with the options already defined.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>