socket: disallow CBC cipher modes

This is related to CVE-2014-3566 a.k.a. POODLE.

	http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-3566

POODLE is specific to CBC cipher modes in SSLv3.  Because there is no
way to prevent SSLv3 fallback on a system with an unpatched version of
OpenSSL, users of such systems can only be protected by disallowing CBC
modes.  The default cipher-mode specification in our code has been
changed accordingly.

cherry picked from http://review.gluster.org/#/c/8962/
BZ 1155328

Change-Id: Id38a7eb3ab55058a0ee5dda9cb4c62b49b1ab9cb
BUG: 1155630
Signed-off-by: Kaleb S. KEITHLEY <kkeithle@redhat.com>
Reviewed-on: http://review.gluster.org/8967
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>