wic: ensure generated disk system identifier is non-zero

Zero may be interpreted as no MBR signature present and another
partitioning program might install a new MBR signature.

(From OE-Core rev: f53b5555d6eaa171bc5882cfee807cf62576862d)

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/plugins/imager/direct.py

@@ -303,7 +303,7 @@ class PartitionedImage():
                           # all partitions (in bytes)
         self.ptable_format = ptable_format  # Partition table format
         # Disk system identifier
-        self.identifier = int.from_bytes(os.urandom(4), 'little')
+        self.identifier = int.from_bytes(os.urandom(4), 'little') or 0xffffffff
 
         self.partitions = partitions
         self.partimages = []