gtphub: handle Delete PDP Context.

During resolution of the header TEI, also return the tunnel struct that
resolved the TEI, so the Delete PDP Ctx code does not need to look it up
again.

Upon Delete PDP Ctx Request, remember the IEs and that a request was made.
Upon Delete PDP Ctx Response, find the pending delete and remove the
corresponding tunnel, iff the response indicates success.

Add a context deletion to regression tests, rename the test appropriately.

Sponsored-by: On-Waves ehi
diff --git a/openbsc/tests/gtphub/gtphub_test.ok b/openbsc/tests/gtphub/gtphub_test.ok
index 24b9aad..8f66b9d 100644
--- a/openbsc/tests/gtphub/gtphub_test.ok
+++ b/openbsc/tests/gtphub/gtphub_test.ok
@@ -1,5 +1,5 @@
 test_echo
-test_create_pdp_ctx
+test_one_pdp_ctx
 - __wrap_gtphub_resolve_ggsn_addr():
   returning GGSN addr from imsi 240010123456789 ni internet: 192.168.43.34 port 2123
 test_user_data