In case of successful completion of handover gsm_subscriber_connection could be moved from one bts to another,
so connection link to bts should be replaced by link to bts, which owns new_lchan.
This bug was detected, because conn->bts->nr is used in call control log messages
and wrong number of bts was observed in these messages after handover.
Change-Id: Idc7dd412b7580c451e716b73ef7549826c60b0d9