bsc: release dchan in TC_cbsp_emerg_write_bts_cgi_dchan

A follow-up patch is adding BSC_Tests.f_shutdown_helper() calls to all
CBSP testcases, what makes TC_cbsp_emerg_write_bts_cgi_dchan fail due
to talloc count mismatch.  All dchans need to be released to avoid this.

Change-Id: I8b707c821693f930ab10bd8feea08ba5007da967
2 files changed