Valid KVP getTile Requests respond with a GetCapabilities document

[ianturton]

While debugging some reported GeoServer issues I've discovered that requests like

http://wmts.kartetirol.at/wmts?request=GetTile&tilematrixset=GoogleMapsCompatible&TileRow=1&service=WMTS&format=image%2Fpng&style=default&TileCol=1&version=1.0.0&layer=gdi_summer&TileMatrix=1&

and

https://tileservice.charts.noaa.gov/tiles/wmts?request=GetTile&tilematrixset=GoogleMapsCompatible&TileRow=25&service=WMTS&format=image%2Fpng&style=default&TileCol=17&version=1.0.0&layer=11006_1&TileMatrix=6&

return their getCapabilities document rather than the tile (or even error message). The corresponding RESTFul requests work fine.