pvscan: use quick activation only with matching PV device names

pvscan: use quick activation only with matching PV device names

When the PV device names in the VG metadata do not match the
current PV device names seen on the system, do not use the
optimized activation function (that avoids extra device scanning.)

When the device names do not match, it's a clue that there could
be duplicate PVs, in which case we want to scan all devicess to
find any duplicates and stop the activation if found.

This does not prevent autoactivating a VG from the incorrect
duplicate PV, because the incorrect duplicate may appear by itself
first.  At that point its duplicate PV does not exist to be seen.
(A future enhancement could use the WWID to strengthen this
detection.)