msm: ipa: fix not invoking tethering stats when polling is disabled

When polling is stopped (either by explicit IOCTL or due to Modem
SSR) we need to make sure no polling request will be queued.
In addition, the timeouts of waiting for QMI reply for all tethering
stats related QMI messages has been reduced (To not wait for the
QMI framework timeout, which might be long).

Change-Id: I7729e8bc3356d5bc8a749cc1c70a9af0ae852ee1
Signed-off-by: Sivan Reinstein <sivanr@codeaurora.org>
Acked-by: David Arinzon <darinzon@qti.qualcomm.com>