tools/mgmt-tester: Fix Stop Discovery setup phase completion
tools/mgmt-tester: Fix Stop Discovery setup phase completion

When we request discovery to be started we should wait both for the mgmt
command completion as well as the discovering event. Otherwise the
discovering event may leak to the actual test phase and cause the test
to fail because of an unexpected event.

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