lvmlockd: avoid lockd_vg for local VGs

lvmlockd: avoid lockd_vg for local VGs

Previously, a command would call lockd_vg() for a local VG,
which would go to lvmlockd, which would send back ENOLS,
and the command would not care when it saw the VG was local.
The pointless back-and-forth to lvmlockd for local VGs can
be avoided by checking the VG lock_type in lvmcache (which
label_scan now saves there; this wasn't the case back when
the original lockd_vg logic was added.)  If the lock_type
saved during label_scan indicates a local VG, then the
lockd_vg step is skipped.