rc.newwanip should bail on diabled interfaces
If an interface is disabled, rc.newwanip should not attempt to (re)configure the interface when its link goes down/up.
Currently if you disable an interface and the old settings are in the config, and if you unplug/replug the interface, it will attempt to reconfigure the interface and fail, then it will reset the interface because it failed. This is all unnecessary since the interface should be off/disabled.
If the interface is configured and not enabled, bail. We do not need to change settings for disabled interfaces. Fixes #3313