csip: Allow to lock only connected devices

Before, CSIP required to have all devices connected in the set to
perform lock procedure.
From now on, CSIP will relax and allow to lock only connected devices
as there is no reason for beeing that strict

Bug: 230426955
Test: atest BluetoothInstrumentationTests
Test: atest --host bluetooth_csis_test
Tag: #stability
Change-Id: I88fc3f2a0e7af67cc3ee7e62813ee3ec08434cd9