rootfs-post: remove traling blanks from tasks

remove the traling blanks before the ;-delimiter, so one could use
"_remove" to avoid running tasks like 'rootfs_update_timestamp',
which are currently hardcoded and not bound to any
configurable feature flag

Signed-off-by: Priyal Doshi <pdoshi@mvista.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>