Simplify polling troubleshooting

* introduce enum describing poll kind and use it in set_polling()
* move state change into set_polling()
* move logging into set_polling() and unify output
* move duplicated code into static function
* adjust tests to match unified logging output

Change-Id: I14074207f8bbc18b3ebd60875bb99a0a3a4b399d
Related: OS#1524
diff --git a/src/tbf_ul.cpp b/src/tbf_ul.cpp
index 1e0898a..81d3b24 100644
--- a/src/tbf_ul.cpp
+++ b/src/tbf_ul.cpp
@@ -158,9 +158,8 @@
 	m_contention_resolution_done = 1;
 
 	if (final) {
-		set_polling(new_poll_fn, ts);
+		set_polling(new_poll_fn, ts, GPRS_RLCMAC_POLL_UL_ACK);
 		/* waiting for final acknowledge */
-		ul_ack_state = GPRS_RLCMAC_UL_ACK_WAIT_ACK;
 		m_final_ack_sent = 1;
 	} else
 		ul_ack_state = GPRS_RLCMAC_UL_ACK_NONE;