libmount: always trust the source of a pseudofs

libmount: always trust the source of a pseudofs

Since nodev FSs have no backing block device, it's unreasonable to try
and resolve the source back to a path on the filesystem. Always trust
the source of the FS given in /etc/fstab to avoid remounting the device
when a directory of the same name exists in the current working
directory.

Example reproduction:

  # mkdir /foo
  # echo 'foo  /foo  tmpfs  defaults  0  0' >> /etc/fstab
  # mount -a
  # cd /root; mkdir foo
  # mount -a
  # mount | grep /foo
  foo on /foo type tmpfs (rw,relatime)
  /root/foo on /foo type tmpfs (rw,relatime)

[kzak@redhat.com: - use fs->flags to detect pseudo FS]

Signed-off-by: Dave Reisner <dreisner@archlinux.org>
Signed-off-by: Karel Zak <kzak@redhat.com>