Add "use_locking" parameter to network query opcode

This was extracted from a patch by Dimitris Aragiorgis with the subject
“Add locking to _NetworkQuery”. The rest of the patch did no longer
apply and will require more work.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>