tests: Bluetooth: build host/adv/resume without BT_CENTRAL

For the second test (test_2):
Build the DUT image without BT_CENTRAL.

The Softdevice Controller uses different memory pools for the central &
peripheral roles. In the configuration where BT_CENTRAL=y, BT_PERIPHERAL=y
and BT_MAX_CONN=2, the SDC will only have room for one central and one
peripheral role.

The test then won't pass as it expects the controller to have room for two
peripheral connections, and the SDC ends up with only one.

Signed-off-by: Jonathan Rico <jonathan.rico@nordicsemi.no>