Init of Plugins may fail when ES is not reachable during startup

Maybe we should add a soft wait for ES to prevent such errors? Especially when starting a docker stack the ES may not be up while Mesh already is. Plugins which run search queries may fail during init.

Start by tracing plugin initialization and the search queries run while Elasticsearch is unavailable during startup. Reproduce the failure with a Docker stack where Elasticsearch starts later; done means plugins do not fail during initialization and behave correctly once Elasticsearch becomes reachable.

Written by the indexing model from the issue text.