Recreating HTTPS ingress should work without error

[nikhiljindal]

Fixing the issue where recreating https ingress was failing.

This was happening due to 2 reasons:

• kubemci thought that ingress changed even when it didnt. This was happening because the in cluster ingress had the instance groups annotation. Updated the code to ignore that annotation before comparing the ingresses.
• kubemci thought that SSL cert changed even when it didnt. This was because we were comparing the complete cert, which includes both the cert and the private key. But GCP returns a cert with empty private key (key is write only). Updated the code to compare the certificate only, which is what ingress-gce does as well: https://github.com/kubernetes/ingress-gce/blob/572e8e56a0c6ba15b0eac5ca870416c4c8fdc09c/pkg/loadbalancers/l7.go#L280

cc @csbell @madhusudancs @G-Harmon @bowei