xfs_io: set exitcode on failure appropriately

xfs_io: set exitcode on failure appropriately

Many operations don't set the exitcode when they fail, resulting
in xfs_io exiting with a zero (no failure) exit code despite the
command failing and returning an error. The command return code is
really a boolean to tell the libxcmd command loop whether to
continue processing or not, while exitcode is the actual xfs_io exit
code returned to the parent on exit.

This patchset just makes the code do the right thing. It's not the
nicest code, but it's a start at producing correct behaviour.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>