Updated docker-registry account regex validator

[nthh]

Relevant error in clouddriver:

due to violations [ConstraintViolationImpl{interpolatedMessage='must match "^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$"', propertyPath=metadata.name, rootBeanClass
=class io.fabric8.kubernetes.api.model.Secret, messageTemplate='{io.fabric8.kubernetes.api.model.Pattern.message}'}]

Fixes #2397

[spinnakerbot]

The following commits need their title changed:

e8329fa: Updated docker-registry account regex validator

Relevant error in clouddriver: due to violations [ConstraintViolationImpl{interpolatedMessage='must match "^a-z0-9?(.a-z0-9?)*$"', propertyPath=metadata.name, rootBeanClass
=class io.fabric8.kubernetes.api.model.Secret, messageTemplate='{io.fabric8.kubernetes.api.model.Pattern.message}'}]

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

This allows us to easily generate changelogs & determine semantic version numbers when cutting releases. You can read more about commit conventions here.

[lwander]

Thanks!