verify_dns_name_resolution_after_upgrade - mark node dirty after OS update

After OS upgrade sometimes kernel version may change. When LISA is used to validate a VM image with specific kernel version, changing the kernel will result in running tests with undesired kernel which should be avoided. Marking the node dirty after OS update to avoid such issues.

Author: SRIKKANTH

lisa/microsoft/testsuites/core/dns.py

@@ -67,6 +67,7 @@ def verify_dns_name_resolution_after_upgrade(self, node: Node) -> None:
             raise PassedException(e) from e
 
         finally:
+            node.mark_dirty()
             self._check_dns_name_resolution(node)
             node.reboot()
             self._check_dns_name_resolution(node)