Add flag to make binary image data from curl to go null

ci_tests/_tests_common.sh

@@ -218,7 +218,7 @@ run_mapserver_postgres_checks() {
 run_mapcache_checks() {
     first_time=$(run_remote_curl_pod "${MAPCACHE_RELEASE_NAME}1" "http://${MAPSERVER_RELEASE_NAME}.${ns}/wms_times/g16/abi/radm1/C01" | head -c 21 | tail -c 19)
     debug "MapServer first time: ${first_time}"
-    run_remote_curl_pod "${MAPCACHE_RELEASE_NAME}2" "http://${MAPCACHE_RELEASE_NAME}.${ns}/mapcache/wmts/?TIME=${first_time}Z&TILEMATRIXSET=grid_g16_abi_radf_1000m&LAYER=g16_abi_radm1_l1b_C01&Service=WMTS&Request=GetTile&Version=1.0.0&Format=image%2Fpng&TileMatrix=0&TileCol=0&TileRow=0" --fail >/dev/null
+    run_remote_curl_pod "${MAPCACHE_RELEASE_NAME}2" "http://${MAPCACHE_RELEASE_NAME}.${ns}/mapcache/wmts/?TIME=${first_time}Z&TILEMATRIXSET=grid_g16_abi_radf_1000m&LAYER=g16_abi_radm1_l1b_C01&Service=WMTS&Request=GetTile&Version=1.0.0&Format=image%2Fpng&TileMatrix=0&TileCol=0&TileRow=0" --fail --output - >/dev/null
 }
 
 run_client_checks() {