kubernetes.py: Fix handling of exception during rollback
Avoid the following cascading exception when an exception occurs during rollback:
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/workspace/scap/scap/cli.py", line 723, in run
exit_status = app.main(app.extra_arguments)
File "/workspace/scap/scap/main.py", line 1066, in main
return super().main(*extra_args)
File "/workspace/scap/scap/main.py", line 203, in main
self.k8s_ops.deploy_k8s_images_for_stage(stage)
File "/workspace/scap/scap/kubernetes.py", line 428, in deploy_k8s_images_for_stage
raise e
UnboundLocalError: local variable 'e' referenced before assignment
18:01:11 scap failed: <UnboundLocalError> local variable 'e' referenced before assignment (scap version: 4.110.0) (duration: 00m 33s)