I posted an article https://unifiedit.wordpress.com/2014/03/03/lync-vdi-on-citrix-pooled-vm-and-double-signin-with-vdi-plugin/ who informed that we had an issue with Lync 2013 on VDi with a systematic double authentication each time you opened a Pooled Windows Vdi machine session and launch your Lync client despite you have checked the remind the password check box. (This double authentication is by default present at the first time but should be not present the second time you opened your Lync in Vdi Mode)
The issue has been solved today by using the Citrix UPM (http://www.citrix.com/go/jmp/upm.html) functionality
Thanks to Marion Dine for her tests and her determination
Regards
Laurent Teruin