mgr/vol: don't delete user-created pool in "volume create" command

mgr/vol: don't delete user-created pool in "volume create" command

If one of the pool names passed to "ceph fs volume create" command
(through --data-pool and --meta-pool name) is absent, don't delete the
pool that is present and passed to this command during the cleanup code
of this command.

IOW, "volume create" command should continue deleting pool created by it
but not delete pool created by the user.

Fixes: https://tracker.ceph.com/issues/70945
Signed-off-by: Rishabh Dave <ridave@redhat.com>
(cherry picked from commit 4299f660ba9c83ef9305b2834c195da9008810a9)