pvmove: prohibit non-resilient collocation of RAID SubLVs

pvmove: prohibit non-resilient collocation of RAID SubLVs

'pvmove -n name pv1 pv2' allows to collocate multiple RAID SubLVs
on pv2 (e.g. results in collocated raidlv_rimage_0 and raidlv_rimage_1),
thus causing loss of resilence and/or performance of the RaidLV.

Fix this pvmove flaw leading to potential data loss in case of PV failure
by preventing any SubLVs from collocation on any PVs of the RaidLV.
Still allow to collocate any DataLVs of a RaidLV with their sibling MetaLVs
and vice-versa though (e.g. raidlv_rmeta_0 on pv1 may still be moved to pv2
already holding raidlv_rimage_0).

Because access to the top-level RaidLV name is needed,
promote local _top_level_lv_name() from raid_manip.c
to global top_level_lv_name().

- resolves rhbz1202497