Support for QLEService::writeCharacteristic() on Android

Currently only the WriteWithResponse mode works and has been tested.

Change-Id: I7947b67f737f5878a01704c09d3a9a532a41b820
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
Fix intermittent failure when mapping handles to services

startHandle and endHandle were randomly initialized and thus
QLowEnergyControllerPrivate::serviceForHandle(..) failed at the same
rate.

In addition this adds a few debug logs which turned out useful when
debugging the above issue.

Change-Id: I41b65274213a66fa100d8c69bba02be0bb876b65
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>