esoc: Wait for modem status to go low in crash shutdown

Wait for modem status to go low in crash shutdown. This helps
cover the race condition where there is a crash during graceful
shutdown and we end up in crash path and send crash notification
to clients even before the modem status has gone low.

Change-Id: I680b79c7a1de5e44cb9fcfa0f9d67517c0398f62
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>