mtk: Fix slow socket disconnection in FM

When unsetting flight mode, rild usually closes the sockets, but this does not necessarily happens always. In some cases this disconnection is notified to ofono a bit too late, which leaves ofono in a bad state. This change adds a timeout so in case we actually expect the sockets to be closed we slow down the sequence of ofono actions lo leave time for the notification to happen.
My suggested re-wording of your comment is:

MTK's rild behavior when a POWERON is sent to it is different
depending on whether a previous POWEROFF had been sent.  When
the modem is initialized during device startup, POWERNON is
sent without a prior POWEROFF, so rild responds with an OK reply,
and the modem is brought up.  Any subsequent POWERON requests
are sent whenver FlightMode is disabled ( meaning a POWEROFF
has been sent prior ). rild may respond to the POWERON request,
but will ?always? trigger a socket disconnect in this case.

This means there's a race condition between the POWERON reply
callback and the socket disconnect function ( which triggers a
SET_SIM_MODE request ). If the POWERON reply is handled first,
it triggers modem bringup which fails due to the radio not being
available. Once this happens, the modem is left in an inconsistent
state and can no longer be used. So, delay sending the SET_SIM_MODE
for 1s, to allow the disconnect to happen.


Also, I didn't mention the SIGPIPE crash... instead if it's still possible for a SIGPIPE to crash ofono, we should file a bug, and fix the crash.