Handle packet access reject during EPDAN/PDAN with channel description

When PDAN/EPDAN with channel description is received, PCU will generate the
packet access reject if no resources are present. The encoding is done
based on section 7.1.3.2.1 and 8.1.2.5 of 44.060 version 7.27.0 Release 7.
This patch also includes the test case to validate the generated
packet access reject message.

This patch is integration tested on Osmo-trx setup with Ettus B210 board
and LG F70 MS with some simulation code changes in Osmo-pcu.

Change-Id: I096a3bb44a65533b9e9b091925dd5f70a8696d6
diff --git a/tests/tbf/TbfTest.ok b/tests/tbf/TbfTest.ok
index f921dfc..dc07fc7 100644
--- a/tests/tbf/TbfTest.ok
+++ b/tests/tbf/TbfTest.ok
@@ -72,3 +72,6 @@
 === end test_immediate_assign_rej_multi_block ===
 === start test_immediate_assign_rej_single_block ===
 === end test_immediate_assign_rej_single_block ===
+=== start test_packet_access_rej_epdan ===
+packet reject: 40 84 7f f7 6e e6 41 4b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
+=== end test_packet_access_rej_epdan ===