vmupdate: fix kernels cleanup in apt_cli

Fixes: 0d25c99 "updater: remove obsolete kernels from debian"

Author: marmarek

vmupdate/agent/source/apt/apt_cli.py

@@ -128,7 +128,7 @@ def remove_obsolete_kernels(self) -> ProcessResult:
                 cmd = [self.package_manager, "remove", "-y", *obsoletes]
                 result = self.run_cmd(cmd, realtime=False)
             else:
-                result = ProcessResult.OK
+                result = ProcessResult(EXIT.OK)
 
         result.code = EXIT.ERR_VM_CLEANUP if result.code != 0 else 0
-        return result
+        return result