BUG/MINOR: ssl: fix build without SSL

Commits 222a7c6 and 150bfa8 introduced some SSL initialization in
bind_conf_alloc() which broke the build without SSL.

Issue #322.
diff --git a/include/proto/listener.h b/include/proto/listener.h
index 3648882..2336e63 100644
--- a/include/proto/listener.h
+++ b/include/proto/listener.h
@@ -157,10 +157,11 @@
 	bind_conf->xprt = xprt;
 	bind_conf->frontend = fe;
 	bind_conf->severity_output = CLI_SEVERITY_NONE;
+#ifdef USE_OPENSSL
 	HA_RWLOCK_INIT(&bind_conf->sni_lock);
 	bind_conf->sni_ctx = EB_ROOT;
 	bind_conf->sni_w_ctx = EB_ROOT;
-
+#endif
 	LIST_INIT(&bind_conf->listeners);
 	return bind_conf;
 }