icnss2: Ignore server exit if already in progress

This change is to avoid back to back server exit/arrive call
from qmi framework. It also ensures that server arrive is
processed only after releasing qmi handle after SSR/PDR.

Change-Id: I8f798fa5fa16a2754d312fc22e20e6bba2fe02e5
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>