bug: secret controller doesn't update ApisixTls but just re-push the old one

[tokers]

Issue description

Secret controller doesn't update the ApisixTls resources when the related secret resource was changed.

Though the related ApisixTls resources will be re-pushed to APISIX cluster, the content was not changed.

Environment

• your apisix-ingress-controller version (output of apisix-ingress-controller version --long); master branch
• your Kubernetes cluster version (output of kubectl version);
• if you run apisix-ingress-controller in Bare-metal environment, also show your OS version (uname -a).

Minimal test code / Steps to reproduce the issue

What's the actual result? (including assertion message & call stack if applicable)

What's the expected result?

[tokers]

Fixed.