a_iface: fix BSSMAP reset handling

When osmo-msc restarts it looses all information about the BSC. The
BSC will not be aware of the reboot and on the next communication
attemt it will notice that something is wrong and start the reset
procedure on his side. osmo-msc will receive the reset messages
and send a reset.

The reset is received. Osmo-msc detects that no context information
is created yet. The context is created. Then it is checked if the
UNITTDATA message that came in is a reset. If it is one. Nothing
happens. The UNITTDATA is passed on and triggers the RESET-ACK
some layers above. Unfortunately by the current code this also
means that no reset FSM is created and therefore a_reset_conn_ready()
can never be true. Which means it will also drop any legitimate
reset from the BSC in the future.

- Ensure that the reset FSM is always created when a new BSC
  context is created

- Make sure that reset related traffic always passes so that
  the higher layers can handle the procedure properly

Change-Id: I3fdcec5dbeaa0e21fd6a92568a623faa368239be
1 file changed