Fix documentation build
Fix documentation build

manila/share/drivers/emc/plugins/registry.py was removed which leads to:

ImportError: No module named registry

while generating the documentation.

Change-Id: I3527e6bd37f56e5b1cbae0bdccd64487871ea560

openstack/manila,jcsp/manila,bswartz/manila,redhat-openstack/manila,weiting-chen/manila,vponomaryov/manila,scality/manila,redhat-openstack/manila,bswartz/manila,scality/manila,NetApp/manila,weiting-chen/manila,NetApp/manila,sajuptpm/manila,sajuptpm/manila,openstack/manila,jcsp/manila,vponomaryov/manila