Set default cow_mountopt where the other defaults are used.

Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>

scripts/live

@@ -1109,6 +1109,7 @@ setup_unionfs ()
 	else
 		cowdevice="tmpfs"
 		cow_fstype="tmpfs"
+		cow_mountopt="rw,noatime,mode=755"
 	fi
 
 	if [ "${cow_fstype}" = "nfs" ]
@@ -1118,8 +1119,6 @@ setup_unionfs ()
 		nfsmount ${nfs_cow_opts} ${cowdevice} /cow || \
 			panic "Can not mount ${cowdevice} (n: ${cow_fstype}) on /cow"
 	else
-		# make sure cow_mountopt is set:
-		[ -n "$cow_mountopt" ] || cow_mountopt="rw,noatime,mode=755"
 		mount -t ${cow_fstype} -o ${cow_mountopt} ${cowdevice} /cow || \
 			panic "Can not mount ${cowdevice} (o: ${cow_fstype}) on /cow"
 	fi