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

Change-Id: Ic9bc0381ed18d37b55cf1fbc49663cbb611ff328
Signed-off-by: Seonah Moon <seonah1.moon@samsung.com>