live: fix error report in partition and format

Fix error codepath and properly mark the operation as failed.

src/live/ogOperations.py

@@ -531,7 +531,7 @@ class OgLiveOperations:
             else:
                 err = mkfs(fs, disk, partition)
 
-            if err == -1:
+            if err != 0:
                 raise OgError(f'Failed to format {part["partition"]} with filesystem {part["filesystem"]}')
 
         ret = subprocess.run(['partprobe', f'/dev/{diskname}'])