MSC_Tests: Reply to Classmark Req in TC_lu_imsi_auth_tmsi_encr_3_1_no_cm

After osmo-msc I73c7cb6a86624695bd9c0f59abb72e2fdc655131, osmo-msc
sends a BSSMAP Classmark Request if encounters a missing Classmark,
which is the case during LU when A5/3 is enabled.

Fix this test by answering the Classmark Request, if any.

Change-Id: I25578c050b7e105ed71b064891d4cd418ee30fcf
2 files changed