DRW: Make profiling more precise on certain drivers.

This makes the whole rendering slower (because of sync point) but the
numbers displayed by the draw manager profiler is more precise on some
buggy drivers. They seems to issue the query before the last one ends.

source/blender/draw/intern/draw_manager_profiling.c

@@ -126,6 +126,7 @@ static void drw_stats_timer_start_ex(const char *name, const bool is_query)
 				glGenQueries(1, timer->query);
 			}
 
+			glFinish();
 			/* Issue query for the next frame */
 			glBeginQuery(GL_TIME_ELAPSED, timer->query[0]);
 			DTP.is_querying = true;