lvchange: Allow device specification when requesting a repair
'lvchange --resync LV' or 'lvchange --syncaction repair LV' request the
RAID layout specific parity blocks in raid4/5/6 to be recreated or the
mirrored blocks to be copied again from the master leg/copy for raid1/10,
thus not allowing a rebuild of a particular PV.
Introduce repeatable option '--[raid]rebuild PV' to allow to request
rebuilds of specific PVs in a RaidLV which are known to contain corrupt
data (e.g. rebuild a raid1 master leg).
Add test lvchange-rebuild-raid.sh to test/shell doing rebuild
variations on raid1/10 and 5; add aux function check_status_chars
to support the new test.