create_context_ind(): ignore any non-started APNs

If we receive a GTP-C CREATE PDP CONTEXT for an APN that we were
unable (or not configured) to start, ignore that APN.

Change-Id: I8011a9ccc1d5effd3779f184c9055af46838ccaf
diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index c1f0c1a..dd71957 100644
--- a/ggsn/ggsn.c
+++ b/ggsn/ggsn.c
@@ -447,6 +447,9 @@
 
 	/* First find an exact APN name match */
 	apn = ggsn_find_apn(ggsn, name_buf);
+	/* ignore if the APN has not been started */
+	if (!apn->started)
+		apn = NULL;
 	/* then try default (if any) */
 	if (!apn)
 		apn = ggsn->cfg.default_apn;