fix pcu_if_signal_cb(): do not send INFO.ind if PCU is not connected
fix pcu_if_signal_cb(): do not send INFO.ind if PCU is not connected

Sending INFO.ind unconditionally in pcu_if_signal_cb() provokes
a lot of warnings during OML bootstrapping / termination:

  DPCU INFO pcu_sock.c:247 Sending info
  DPCU INFO pcu_sock.c:262 BTS is up
  DPCU INFO pcu_sock.c:205 (bts=0,trx=0) unavailable for PCU (op=Disabled adm=Unlocked)
  DPCU INFO pcu_sock.c:205 (bts=0,trx=1) unavailable for PCU (op=Disabled adm=Unlocked)

Do not call pcu_tx_info_ind() if the PCU is not connected.

Change-Id: If8bc8bec5ad808be8d40e91278a4a4fde84920b0

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts