Fix the retry logic in fifloader.py

subprocess.run raises an exception by default if the command
fails, you don't have to look for the return code.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

fifloader.py

@@ -342,15 +342,15 @@ def run(args):
         loadargs.append('-')
         tries = 20
         while True:
-            ret = subprocess.run(loadargs, input=json.dumps(out), text=True, check=True)
-            if ret.returncode:
+            try:
+                subprocess.run(loadargs, input=json.dumps(out), text=True, check=True)
+                break
+            except subprocess.CalledProcessError:
                 if tries:
                     print(f"loader failed! retrying ({tries} attempts remaining)")
                     tries -= 1
                 else:
                     sys.exit("loader failed and all retries exhausted!")
-            else:
-                break
 
 def main():
     """Main loop."""