www/phpvirtualbox: Set default cookie expiry date to 7 days after creation

Fix the issue "unable to switch servers"
A few weeks ago phpVirtualBox started preventing users to switch from one
server to another, as you can read in this upstream bug report:
https://github.com/phpvirtualbox/phpvirtualbox/issues/267

PR: 253155
Submitted by: andrew.hotlab
With hat: ports-secteam
Obtained from: phpvirtualbox repo
MFH: 2021Q1