server: avoid deadlock
server: avoid deadlock

  peer.configuredRFlist() uses lock in itself.

a16/gobgp,a16/gobgp,a16/gobgp,tamihiro/gobgp,osrg/gobgp,fujita/gobgp,j-kato/gobgp,osrg/gobgp,a16/gobgp,a16/gobgp,fujita/gobgp,a16/gobgp,osrg/gobgp,tamihiro/gobgp,fujita/gobgp,a16/gobgp,j-kato/gobgp,tamihiro/gobgp,j-kato/gobgp,fujita/gobgp,osrg/gobgp,tamihiro/gobgp