qa/cephfs: create new class for "volume fs volume rename" tests

qa/cephfs: create new class for "volume fs volume rename" tests

Move tests for "ceph fs volume rename" command to a new class. This
makes it possible to run this group of tests in a single command.

This provides a convenient way to execute these tests which is necessary
after the changes has been made to the code for the "ceph fs volume
rename" command.

Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit e268908a5a0d9954c71ee3e2d3e5606df0a19c59)

Conflicts:
	qa/tasks/cephfs/test_volumes.py
	test_rename_when_fs_is_online() is not present on Quincy branch,
	unlike main branch