Users can visit more than one ticket via link

Previously, once a client was authenticated to the system with an email
link, the user could utilize other email links to other tickets; however,
the same ticket page would be presented to the user regardless of which link
was utilized.

This patch allows the ticket in focus for the user to be changed after
visiting the client portal with a different ticket link.
Merge pull request #1001 from greezybacon/issue/client-change-tickets

Users can visit more than one ticket via link

Reviewed-By: Peter Rotich <peter@osticket.com>