Changes

Fix SCCP RLSD not sent upon rx RUA Disconnect due to error condition

Scenario: HNB tears down the RUA/Iu conn by first sending
RUA_DATA[RANAP IuReleaseReq], followed shortly by a RUA Disconnect with no
RANAP and Cause!=Normal. HNBGW should release the SCCP connection through
RLSD since it's impossible to terminate the Iu connection in a normal
condition.

Validated with TTCN-3 HNBGW_Tests.TC_cs_iu_release_req_rua_disconnect.

Related: osmo-ttcn3-hacks.git Change-Id I6782920c4a86d3311eb54239ab13a18e393c1ec0
Related: SYS#6602
Change-Id: I1b7f72034eaf40bfa60d552d434847467ac4e97a