souphttpsrc: Initialize return variable

In the normal use-case we would end up with ret being unitialized
causing havoc.

https://bugzilla.gnome.org/show_bug.cgi?id=777222

ext/soup/gstsouphttpsrc.c

@@ -1649,7 +1649,7 @@ static GstFlowReturn
 gst_soup_http_src_create (GstPushSrc * psrc, GstBuffer ** outbuf)
 {
   GstSoupHTTPSrc *src;
-  GstFlowReturn ret;
+  GstFlowReturn ret = GST_FLOW_OK;
   GstEvent *http_headers_event = NULL;
 
   src = GST_SOUP_HTTP_SRC (psrc);