wic: add Disk._put_part_image method

This method copies partition image into the wic image.
It will be used in 'wic cp' and 'wic rm' subcommands
to copy changed partition back into wic image.

(From OE-Core rev: 7a7e6635e2e2ddfff2bca58c860634b7a199b0df)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/engine.py

@@ -300,6 +300,11 @@ class Disk:
 
         return self._partimages[pnum]
 
+    def _put_part_image(self, pnum):
+        """Put partition image into partitioned image."""
+        sparse_copy(self._partimages[pnum], self.imagepath,
+                    seek=self.partitions[pnum].start)
+
     def dir(self, pnum, path):
         return exec_cmd("{} -i {} ::{}".format(self.mdir,
                                                self._get_part_image(pnum),