[Bluetooth] destroyBonding API : remove device from known_devices array

When remote device is unpaired, known_devices array has to be removed as well
and not just isBonded device property.

Add also an error case to directly returns an error if device to unpair is not in
known_devices array.
[Bluetooth] do not return in C API callbacks

This ensures to always execute javascript async post messages and so do
not infinitely wait for backend post messages.
This would prevent from freezing xwalk in some cases.

BUG=XWALK-2491
Merge pull request #386 from eurogiciel-oss/destroyBonding

Destroy bonding + C API callbacks not return