How to reset the Lync 2013 client sign in after mass SIP changes

If you change your users SIP address, the next time they login the old SIP address will still be the sign in address.  This may confuse them and generate needless tickets.  By using a logon script to clear this value, the problem is solved:  HKCU\software\Microsoft\office\15.0\lync\serversipuri

This will populate the sign in with the SIP address from AD the next time Lync is started.