Missing es shouldn't block other apps

[spalger]

Fixes elastic/sense#77

When deciding if an app or the status page should be rendered we check if any plugin is red. Instead, we should only see if the app's plugin is red or any of the plugins that app requires are red.

This would still prevent us from showing the Kibana app when elasticsearch is unavailable but would not prevent us from showing the Sense app since it does not require the elasticsearch plugin.

[spalger]

Duplicate of #5300