blkid: Make regression test tolerate older versions of mkswap

blkid: Make regression test tolerate older versions of mkswap

The blkid/tests contains new tests for swap, but the type-1 swapfile
test depends on mkswap supporting the "-U" option to specify the UUID.
This is not available even on relatively recent versions of mkswap
(2.13.1 16-Jan-2008) so the test needs to be changed to handle this.
If the "-U" option is not supported, don't verify the UUID in the blkid
output during testing.

Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>