tests/meas: improve test_ts45008_83_is_sub_is_sub()
tests/meas: improve test_ts45008_83_is_sub_is_sub()

This function should also take lchan type into account.

Change-Id: I6920a04e0a6c846647fa1b6b3a3c80bbd6617b99
Related: SYS#5853

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts