Avoid re-connecting to a new BSC while BTS is in shutting down. All the
FSMs are complex enough to even try to re-start when stopping has not
yet finished...
Change-Id: I1727828a16f4ec8043b00cc6b2e02a4c35f71377
Setting the phy link of a trx to SHUTDOWN sets operative state to
DISABLED, so we use operative state as a condition to know whether all
TRX are already powered off properly and we can exit.
Change-Id: I2bcd211d7edcc8486461a555d6c470a94b166ed7
Upon BTS shutdown (for instance because the Abis link against BSC was
lost), stop the operation in an ordered manner (cell soft lock). This
means slowly decrease tx power so that MS have time to handover to other
neighbour cells.
Related: SYS#4920
Change-Id: I70e34dda8974ebd94aea33bd9fb1d99f9063cc55
Using an FSM here will allow for more complex ordered shutdown
procedures, like power ramp down, waiting for TRX deact asyncrhonously,
etc.
Current commit leaves everything in place already prepared to implement
ramp down, which will be implemented in next commit in the series.
Related: SYS#4920
Change-Id: I8f48f17e61c3b9b86342eaf5b8a2b1ac9758bde5