Searchbox missing after setup

This may have to do with #430, but i could not confirm that.

I have set up FTS with elasticsearch in a docker-container (based on elasticsearch:6.5.0), and it works fine if i enable and use the global search icon. However, the "normal" fts-search does not work, it is still the nextcloud-native searchicon without the popupmenu and all that stuff.
This was tested on two different systems. (Both use elastic in a dockercontainer, and nextcloud&mysql native on the hostsystem)

I noted the following:
I migrated System B to a different server, and got the cloud working again with the db and stuff. Then i enabled FTS, but had not yet finished creating the dockercontainer for elasticsearch. The icon was there, but (obviously) not working. I then proceeded to build the container, and as soon as sudo -u www-data php /var/www/nextcloud/occ fulltextsearch:test stopped returning an error that elasticsearch was down, the fts-icon was replaced by the native searchicon.

There is no additional logging available, neither the client nor the server.
If you need more information, ask me :)

Start by reproducing the setup with Elasticsearch in Docker and run sudo -u www-data php /var/www/nextcloud/occ fulltextsearch:test as the service becomes available. Trace how the FTS and native search icons are selected after the test succeeds; done means the normal searchbox shows the FTS popup instead of the native search icon.