mount: do not guess bind mounts as nfs

Fails as follows:

$ mount -o bind /dev/disk/by-path/pci-0000:13:00.0-scsi-0:0:3:0 /dir
mount: bad address '/dev/disk/by-path/pci-0000'

function                                             old     new   delta
singlemount                                         1256    1273     +17

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed