Extend _require_xfs_io_command so that we can pass it a command line
argument to look for, and then use new capabililty in the relevant
tests to ensure that bmap knows how to dump CoW fork contents (bmap -c)
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>