btrfs-progs: report failure when resize ioctl fails

btrfs-progs: report failure when resize ioctl fails

The BTRFS_IOC_RESIZE ioctl returns 0 on success, negative for POSIX
errors, and positive for btrfs-specific errors.

If resize fails with a btrfs-specific error, decode the error and
report it.  If we can't decode the error, report its numeric value so
that the userspace tool is not instantly useless when a new error code
is defined in the kernel.

Exit with non-zero status on any resize error.  This is very important
for scripts that will shrink the underlying storage when btrfs reports
success!

Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org
Signed-off-by: David Sterba <dsterba@suse.cz>