wifi(implementation): Increase stop timeout

The current timeout of 50ms seems to be insufficient on some devices.
So, changing it to a higher value.

Bug: 66334487
Test:  Ran the VTS tests continously in a loop for 30 minutes
without failure. Previously, failure occurence was about once every
5-10 minutes.
`while adb shell /data/VtsHalWifiSupplicantV1_0TargetTest; do :;
done; adb bugreport`

Change-Id: I884de64d748b46b9710a702f3c72cc30dd51627e