MINOR server: Restrict dynamic cookie check to the same proxy.

Each time we generate a dynamic cookie, we try to make sure the same
cookie hasn't been generated for another server, it's very unlikely, but
it may happen.
We only have to check that for the servers in the same proxy, no, need to
check in others, plus the code was buggy and would always check in the
first proxy of the proxy list.
diff --git a/src/server.c b/src/server.c
index 23343d8..6070de9 100644
--- a/src/server.c
+++ b/src/server.c
@@ -135,18 +135,17 @@
 	 * Check that we did not get a hash collision.
 	 * Unlikely, but it can happen.
 	 */
-	for (p = proxy; p != NULL; p = p->next)
-		for (tmpserv = proxy->srv; tmpserv != NULL;
-		    tmpserv = tmpserv->next) {
-			if (tmpserv == s)
-				continue;
-			if (tmpserv->cookie &&
-			    strcmp(tmpserv->cookie, s->cookie) == 0) {
-				Warning("We generated two equal cookies for two different servers.\n"
-				    "Please change the secret key for '%s'.\n",
-				    s->proxy->id);
-			}
+	for (tmpserv = p->srv; tmpserv != NULL;
+	    tmpserv = tmpserv->next) {
+		if (tmpserv == s)
+			continue;
+		if (tmpserv->cookie &&
+		    strcmp(tmpserv->cookie, s->cookie) == 0) {
+			Warning("We generated two equal cookies for two different servers.\n"
+			    "Please change the secret key for '%s'.\n",
+			    s->proxy->id);
 		}
+	}
 }
 
 /*