cnss2: Release qmi handle after server exit

Release qmi handle after server exit which will help
cnss2 driver to bail out pending qmi transactions gracefully.
QMI server calls server exit whenever a client tries to
release qmi handle and calls server arrive whenever a
client tries to register for service and service is up.
This change also ensures the next server arrive is processed
only when earlier server exit has been processed successfully.

Change-Id: Ia3332694c769731a36bfdb6d7136a3115f5159e4
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>