More fixes. Type "auto" should mean unspecified from fstab as well as the

More fixes.  Type "auto" should mean unspecified from fstab as well as the
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.