Implement mgmt start and stop discovery
Implement mgmt start and stop discovery

This patch implements mgmt_start_discovery and mgmt_stop_discovery
callbacks for mgmtops.

silent-snowman/bluez,ComputeCycles/bluez,pkarasev3/bluez,pkarasev3/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,silent-snowman/bluez,mapfau/bluez,silent-snowman/bluez,ComputeCycles/bluez,ComputeCycles/bluez,silent-snowman/bluez,mapfau/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez