bootc: Exit with rpm-ostree's return code

This is necessary if we want to support rpm-ostree's `--pending-exit-77`
flag. Maybe a cleaner solution could be to bring over libdnf5's
`SilentCommandExitError(int exit_code)`.

plugins/bootc.py

@@ -211,5 +211,4 @@ def configure(self):
     def run(self):
         proc = subprocess.Popen(self.extargs, stdout=sys.stdout, stderr=sys.stderr)
         proc.wait()
-        if proc.returncode != 0:
-            raise dnf.cli.CliError
+        sys.exit(proc.returncode)