TEST: Re-add testing of lvconvert-raid for kernels < 3.2

TEST:  Re-add testing of lvconvert-raid for kernels < 3.2

I'm not sure what 'BUG's were being encountered when the restriction
to limit lvconvert-raid.sh tests to kernels > 3.2 was added.  I do know
that there were BUG's that could be triggered when testing snapshots and
some of the earliest DM RAID available in the kernel.  I've taken out
the 3.2 kernel restriction and added a dm-raid >= 1.2 restriction instead.
This will allow the test to run on patched production kernels.