Commit
f2dc0d185e34d52ad10169f4e5bc076bff05ba55
by lynxisgprs_ns2_sns: fix error cases of SNS_ADD
When adding a NS-VC fails, the SNS-ACK with failure code should follow,
but no second SNS-ACK.
Related: OS#6611
Change-Id: I06bc2622f89256d9675e29b49acc7a3e0647eeae