[Maps] 2 _search requests occur when adding a filter to maps application

[nreese]

Steps to reproduce:

1. Create map with single document layer from web logs.
2. Open web browser developer tools network tab and clear requests.
3. Create a filter pill.
4. Notice how 2 ES requests are made.

The problem occurs in because setQuery is getting called twice in map controller

1. Once in the on-filters-updated callback for SearchBar, https://github.com/elastic/kibana/blob/7.6/x-pack/legacy/plugins/maps/public/angular/map_controller.js#L245
2. Again, in the listener when app_state changes https://github.com/elastic/kibana/blob/7.6/x-pack/legacy/plugins/maps/public/angular/map_controller.js#L95

Vector layer canSkipSourceUpdate does not catch the double request because of the await. Both requests check for changes from the same data request meta.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)