tools/mgmt-tester: increase max adv inst
tools/mgmt-tester: increase max adv inst

The kernel now allows for up to five concurrent advertising instances.
This patch adapts the tests to the new setting.

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