Changes

trx_toolkit/transceiver: Use with tx_queue_lock instead of manual acquire/release

- it is a bit faster
- it is a bit more robust as the lock becomes released in case
  some exception is raised before reaching release

Noticed while moving forwarding out of tx_queue_lock in
I7d10c972c45b2b5765e7c3a28f8646508b3c8a82.

Change-Id: I74b194120bcc518d44796b57e36368bdc8de4aab