Script enables errexit option (set -e). So if /boot is not a mount point
or is already mounted, then script dies after unsuccessful mount
command. Fix this by always returning successful result.
Dracut claims to have LZ4 support, but trying to use it will result in an xzcat failure at the end due to missing CAT support.
The lz4 command chokes on '--', so abstract that out into the CAT select.
Something similar will need to be done for LZO.
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>