[test] Remove some ref images from random-intersections

Each one is larger than 100kb, so paint background black to reuse
same ref image for rgb24 and argb32 cases.  Also remove Quartz ref
images for now.

test/Makefile.am

@@ -317,10 +317,7 @@ REFERENCE_IMAGES = \
 	push-group-svg-argb32-ref.png	\
 	radial-gradient-ref.png	\
 	random-intersections-ps-argb32-ref.png	\
-	random-intersections-quartz-ref.png	\
-	random-intersections-quartz-rgb24-ref.png	\
 	random-intersections-ref.png	\
-	random-intersections-rgb24-ref.png	\
 	rectangle-rounding-error-ref.png	\
 	rectilinear-stroke-ref.png	\
 	rel-path-quartz-ref.png	\

test/random-intersections.c

@@ -51,6 +51,10 @@ static cairo_test_status_t
 draw (cairo_t *cr, int width, int height)
 {
     int i;
+
+    cairo_set_source_rgb (cr, 0, 0, 0);
+    cairo_paint (cr);
+
     state = 0x12345678;
     cairo_translate (cr, 1, 1);
     cairo_set_fill_rule (cr, CAIRO_FILL_RULE_EVEN_ODD);