Fix missing exit code in nomededia

nodemedia was not setting return code on exit properly.

confluent_client/bin/nodemedia

@@ -193,5 +193,7 @@ def main():
         argparser.print_help()
         sys.exit(1)
     handler(noderange, media)
+
 if __name__ == '__main__':
     main()
+    sys.exit(exitcode)