[hotfix] reduce the interval btw/ welcome message & setting expiry time

context:

• sometimes the expiry update arrives before (or instead of!) the welcome message which is either confusing or very bad
• for that reason, we had set a delay between welcome and expiry setting of minResendInterval
• minResendInterval used to be 2 sec, but now it is 60 sec

changes

• this MR creates a separate config (setExpiryInterval) for the delay for the first expiry update, and sets it to 2 sec (as before)