allow disable wildcard host with https redirect

When setting up keycloak with a tls passthrough gateway, we don't want a wildcard server host entry, but the chart provides no way to disable the default entry.

https://repo1.dso.mil/platform-one/big-bang/apps/core/istio-controlplane/-/blob/fc109ca38ab492dd380f20f99f6ff44230afda20/chart/templates/gateway.yaml

Lines 16-23 need to be able to be turned off with a value.