command line, initialize singlemount's rc to an error value so it doesn't
think it succeeded when it didn't, use absolute path when associating a
loop device (and the previous FEATURE_CLEAN_UP logic related to that was
freeing the wrong thing), move reading of /proc/filesystems to where we can
re-read it (when it's empty) for every entry on a "mount -a" so that when
/proc is mounted as the first entry, the later filesystems can autodetect
filesystem type.
eaa34ca5b4