Annotations: Allow ciphers with underscores.

[steve21168]

The ingress annotation nginx.ingress.kubernetes.io/ssl-ciphers is disallowing valid ciphers that have an underscore.

The nginx documentation - states about valid ciphers:

The full list can be viewed using the “openssl ciphers” command.

From the latest official image: registry.k8s.io/ingress-nginx/controller:v1.12.1@sha256:d2fbc4ec70d8aa2050dd91a91506e998765e86c96f32cffb56c503c9c34eed5b

$ openssl ciphers
TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:....

What this PR does / why we need it:

It allows for valid SSL ciphers with underscores.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] CVE Report (Scanner found CVE and adding report)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation only

Which issue/s this PR fixes

How Has This Been Tested?

Yes via the validation unit test

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I've read the CONTRIBUTION guide
• [x] I have added unit and/or e2e tests to cover my changes.
• [x] All new and existing tests passed.

If this is considered to be accepted I can go fill out the CLAs.