* ClientInterface: add a function to verify (correctly) if user limit was reached
CS_HelloSent is a better indicator of active slots than CS_Created, which are session objects created after init packet reception
Switch existing checks to ClientInterface::isUserLimitReached()
Use range-based for loop for getClientIds() used function too
This will fix#6254 (not the memory overhead if init is flooded)
1d8d01074f