trigger_geocode() should zoom before panning

Problem/Motivation

If the initial zoom is way smaller than the focus zoom, the first time trigger_geocode() is called the panning will be slightly off.
It seems to happen because Leaflet will pan with the initial zoom (which is low so the panning does not have to be super precise) and then zoom.

Steps to reproduce

1. Use a geofield_map widget with Leaflet.
2. Select a town in the autocomplete field.
3. The map zooms and pans slight out of town.

Proposed resolution

setZoomToFocus() should be called before mapSetCenter().
This way, when the panning happens, it already knows at what zoom level the marker should be into view.

Remaining tasks

I will submit a patch.