Xnest: fix upstream visuals retrieval and visual reporting

As upstream might report a huge number of visuals with same parameters,
we have a deduplication mechanism.

This code has a bug: instead of just skipping duplicates, it completely
breaks off once the first duplicate is found - leading to only one depth
supported.

Fixes: adc7f9a4eb
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

hw/xnest/Screen.c

@@ -205,7 +205,7 @@ xnestOpenScreen(ScreenPtr pScreen, int argc, char *argv[])
                 break;
         }
         if (j < numVisuals)
-            break;
+            continue;
 
         visuals[numVisuals].vid = FakeClientID(0);