driver: Fix ganesha config option registry
driver: Fix ganesha config option registry

To register the ganesha config options, the initialization method of
the ShareDriver class incorrectly calls the ExecuteMixin class's
init_execute_mixin() method. Instead call GaneshaMixin's
init_ganesha_mixin() method.

Change-Id: Iafbdcf7ff1701f95e62f444602a5a2d38ad82938
Closes-Bug: #1415738

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