Cinder deprecated the GlusterFS volume driver
in Newton and deleted it in Ocata:
I10c576602dd0e65947d1a1af5d04b8ada54f4625
Since it's unused, unmaintained and unsupported in
Cinder we should remove it from the libvirt driver.
This also removes the related configuration options.
A note is left in the code since I'm unsure if anything
relies on checking for the netfs disk source_protocol which
was added at the same time as the glusterfs support in
Ic6dd861b40b692b25df67c9d5b63fd436c690fde.
Change-Id: I2745f5578646ec994b53f6b5c0a5f62637b0948a
5c5bc57d2b