tls: Only cache session data if a session was not resumed
tls: Only cache session data if a session was not resumed

As per the upstream discussion [1], session data should only be
stored when the session is not resumed.

This affects resuming sessions when using TLS tickets, since they
are not stored in the session data after a save/resume cycle.

[1] http://lists.gnutls.org/pipermail/gnutls-help/2015-February/003760.html

https://bugzilla.gnome.org/show_bug.cgi?id=745099

GNOME/glib-networking,GNOME/glib-networking,GNOME/glib-networking