gsdx-linux: remove an old delay that pollute my benchmark mode

Also add a glFinish to ensure rendering is done

plugins/GSdx/GS.cpp

@@ -1663,14 +1663,16 @@ EXPORT_C GSReplay(char* lpszCmdLine, int renderer)
 					break;
 			}
 		}
+
+		// Ensure the rendering is complete to measure correctly the time.
+		glFinish();
+
 		unsigned long end = timeGetTime();
 		fprintf(stderr, "The %ld frames of the scene was render on %ldms\n", frame_number, end - start);
 		fprintf(stderr, "A means of %fms by frame\n", (float)(end - start)/(float)frame_number);
 
 		stats.push_back((float)(end - start));
 
-
-		sleep(1);
 		finished--;
 		total_frame_nb += frame_number;
 	}