mncc: bts can be NULL, attempt to find the bts from the transaction

Follow trans->conn->lchan to the BTS instead of using the BTS that
is guranteed to be NULL in the codepath we have entered here. The
trans->conn should still be there, and the lchan should be valid as
well as we have reordered the clear statements.
1 file changed
tree: c78c1c7858709747abdc4482ea094d0ece84af03
  1. hlrsync/
  2. linux-kernel/
  3. openbsc/
  4. wireshark/