dont run volume mocks on ci

Author: archmoj

test/image/compare_pixels_test.js

@@ -97,6 +97,7 @@ function untestableFilter(mockName) {
     !(
         mockName === 'font-wishlist' ||
         mockName.indexOf('gl2d_') !== -1 ||
+        mockName.indexOf('gl3d_volume_') !== -1 ||
         mockName.indexOf('mapbox_') !== -1
     );