nokia cosmetic: factor out BTS_CONF_COMPL handling
When the BTS accepts the config sent to it via BTS_CONF_DATA, it responds with BTS_CONF_COMPL. Upon receiving the latter message, we have to send TRX unlock and TRX reset commands, and we have to start LAPD for RSL. Factor out this logic into a helper function, to reduce the level of indentation and make it easier to extend.
