create_storage_ceph and create_storage_netfs wrote the pool, host, user,
secret and format values into the pool XML unescaped and unchecked: the
page's patterns were the only guard, and a direct POST could break or
extend the XML. The values now go through util.xml_escape, as the
network code does. The page's host fields stopped at 20 characters, so
nfs01.storage.example.com could not be typed: they take a host name's
253; the Ceph pool and user fields lose the limit the server never had.
