Add a test for a scenario that used to fail due to find_mount_root()
incorrectly determining the mount point for the receive path due to the
fact that a different mount point with a path that is a prefix of the
receive path exists.
This is fixed by a recent patch titled:
"Btrfs-progs: fix mount point detection due to partial prefix match"
Reported-by: David Disseldorp <ddiss@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
[ adjustments to make the test work when hosted on NFS ]
Signed-off-by: David Sterba <dsterba@suse.com>
