bsc: TC_emerg_premption: check BSSMAP Clear Req cause

On the first TCH, establish Layer 3 so that the BSC will issue a Clear
Request at all.

Verify the cause value of the Clear Request.

Tear down the established Layer 3: clean up for the leak check.

Related: OS#5535
Depends: I20108f7b4769400b89b7b0d65c8dab883bf87c46 (osmo-bsc)
Change-Id: Ib13be73119cfc96712f32899c02e655e1751d547
1 file changed