scripts/live: Make 'nopersistent' parameter actually disable persistence

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

scripts/live

@@ -992,7 +992,7 @@ setup_unionfs ()
 	mkdir -p /cow
 
 	# Looking for "${root_persistence}" device or file
-	if [ -n "${PERSISTENT}" ]
+	if [ -n "${PERSISTENT}" ] && [ -z "${NOPERSISTENT}" ]
 	then
 		cowprobe=$(find_cow_device "${root_persistence}")
 
@@ -1005,7 +1005,7 @@ setup_unionfs ()
 			cowdevice="tmpfs"
 			cow_fstype="tmpfs"
 		fi
-	elif [ -n "${NFS_COW}" ]
+	elif [ -n "${NFS_COW}" ] && [ -z "${NOPERSISTENT}" ]
 	then
 		# check if there are any nfs options
 		if echo ${NFS_COW}|grep -q ','
@@ -1075,7 +1075,7 @@ setup_unionfs ()
 	mount -t tmpfs tmpfs ${rootmnt}/live
 
 	# Adding other custom mounts
-	if [ -n "${PERSISTENT}" ]
+	if [ -n "${PERSISTENT}" ] && [ -z "${NOPERSISTENT}" ]
 	then
 		# directly mount /home
 		# FIXME: add a custom mounts configurable system