Fix Problème couche de fond in Mobile (no background displayed on first
application start) rt#181971

Cherry-pick OpenLayers commit
https://github.com/pgiraud/openlayers/commit/6efcab3d2d4da91f7e9f95974f62cdf521a07a0d
don't try to update the matrix in setMap since it's too early and done later in moveTo
in the cgxp-1.3 comptocamp/openlayers.
Merge pull request #559 from camptocamp/181971

Fix Problème couche de fond in Mobile (no background displayed on first