conpaas: add an explicit warning about snapshoting xtreemfs service.
conpaas: add an explicit warning about snapshoting xtreemfs service.

ConPaaS-team/conpaas,ConPaaS-team/conpaas,ConPaaS-team/conpaas,ConPaaS-team/conpaas,ConPaaS-team/conpaas,ConPaaS-team/conpaas,ConPaaS-team/conpaas