There exists a VTY command for sending default power control params,
but so far there was no CTRL counterpart for it. This patch adds a
SET command 'send-power-control-defaults':
$ osmo_ctrl.py \
--host 127.0.0.1 -p 4249 \
--set "bts.0.send-power-control-defaults" 1
Similar to 'send-new-system-informations', this command takes an
arbitrary dummy value (required for SET), which is simply ignored.
Change-Id: Ib370bd97ee2d9f72f8bec553550b1792d1345387
Related: SYS#6138