bluez5: add an alternative l2pingd tool
This MR is the first part of alternative solution for [YT-72] EMC Bluetooth test
Remaining MRs:
Background: earlier we decided to stick with bluez and obexctl for Bluetooth test. But when a new requirement/clarification appeared that counterpart should be set up without ssh, we realized that it's impossible to switch between master/slave mode for obexctl to provide feedback whether test data was successfully transmitted. So, we decided to rework the test using l2ping tools.
This MR adds a new version of l2pingd tool that can be run in the background.
The tool establishes a connection between a device under test and counterpart. Herewith it will try to restore the BT connection if an error occurs.
During the test we will actively send a SIGUSR1 signal to l2pingd process to invoke pinging of counterpart.