Logger: Output ERR log messages to stderr as well.
Logger: Output ERR log messages to stderr as well.

Signed-off-by: Tom Tsou <072b11b861b7a066437a0a0cead1208995732a66@ettus.com>

ttsou/osmo-trx,kkroo/osmo-trx,ttsou/osmo-trx,kkroo/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,kkroo/osmo-trx,kkroo/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx