The newly introduced Tempest config option,
'capability_snapshot_support' allows glusterfs_native driver
that can support snapshot support to run with snapshot Tempest tests
disabled. Set this option to True to let the glusterfs_native driver
CI not run snapshot tests - the present status-quo of the
glusterfs_native driver CI, and yet succeed to run.
Change-Id: I7e605502a9d6d3a42a26313a7c3bbb53ec08d8bc