Fix T47812: GPU renders have warmer colors than CPU renders

Seems was a mistake in f2c54df, volume attributes are not supposed to
have repeated texture type.

intern/cycles/blender/blender_mesh.cpp

@@ -308,7 +308,7 @@ static void create_mesh_volume_attribute(BL::Object& b_ob,
 	        is_float,
 	        is_linear,
 	        INTERPOLATION_LINEAR,
-	        EXTENSION_REPEAT,
+	        EXTENSION_CLIP,
 	        true);
 }