conf/{checkfs,checkroot-bootclean,checkroot,mountall-bootclean}.sh.conf,
conf/{mountnfs-bootclean,mtab}.sh.conf: additional null jobs for
compatibility with pre-existing sysvinit script names, so that the
sysvinit scripts aren't run.  This speeds up the boot, improves
compatibility with insserv, and guards against e.g.,
mountall-bootclean.sh running after /run is already in use by ifupdown.