The charm exposes no-op options to operators

The manila-ganesha inherits layer:openstack-api on purpose even though it doesn't offer any sort of OpenStack API service.

src/layer.yaml already has the following section not to expose OpenStack API related config options to operators:

config:
  deletes:
    - region
    - ssl_ca
    - ssl_cert
    - ssl_key

However, there are more no-op options exposed namely:

    - haproxy-server-timeout
    - haproxy-client-timeout
    - haproxy-queue-timeout
    - haproxy-connect-timeout
    - dns-ha
    - os-admin-hostname
    - os-admin-network
    - os-internal-hostname
    - os-internal-network
    - os-public-hostname
    - os-public-network

We can avoid confusions by hiding those no-op options.