MEDIUM: proxy: make get_backend_server() use findproxy() to lookup proxies

This one is used by stats to look up proxy and server names in server state
manipulation. Get rid of the linear search.
diff --git a/src/proxy.c b/src/proxy.c
index c2ba2cc..2f2eb49 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -97,22 +97,15 @@
 {
 	struct proxy *p;
 	struct server *s;
-	int pid, sid;
+	int sid;
 
 	*sv = NULL;
 
-	pid = -1;
-	if (*bk_name == '#')
-		pid = atoi(bk_name + 1);
 	sid = -1;
 	if (*sv_name == '#')
 		sid = atoi(sv_name + 1);
 
-	for (p = proxy; p; p = p->next)
-		if ((p->cap & PR_CAP_BE) &&
-		    ((pid >= 0 && p->uuid == pid) ||
-		     (pid < 0 && strcmp(p->id, bk_name) == 0)))
-			break;
+	p = findproxy(bk_name, PR_CAP_BE);
 	if (bk)
 		*bk = p;
 	if (!p)