tests: bsim: Bluetooth: mesh: Adjust test sleep durations

Adjust test sleep durations to compensate towards timing
changes in Zephyr Controller radio scheduling.

With the change in the radio scheduling, there is overlap
of advertising PDU from multiple nodes that relay the PDU,
hence increase test timeout so that next advertising
interval that uses random delay will get received by nodes
without collisions on air.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>