Fix TTCN3 Test BSC_Tests.TC_assignment_sign
The Testcase BSC_Tests.TC_assignment_sign seems to behave incorrectly. It sends an Assignment Request where it requests a signaling only channel SDCCH. Osmo-bsc then decides that is already active is compatible and sends a Channel Mode Modify via RSL, which is never answered. The T10 timeout expires and the assignment fails.
From what I can see, the decision osmo-bsc makes is correct. Also the TTCN3 function f_channel_compatible(ass_cmd.pdu.bssmap.assignmentRequest.channelType, g_chan_nr) that is called from f_establish_fully() comes to the conclusion that the channel is compatible. I am currently lost in the altstep in at the end. I would expect it to continue with as_modify(st) but there I can see none of the steps processed.
From my understanding the behavior of osmo-bsc is correct and the TTCN3 testcase has some malfunction. Attached one finds a trace of the current behavior. See also branch: pmaier/fsm