BUG-632: add initial configuration bits for TCP-MD5

This patch adds the controller-config bit for tcp-md5 and modifies both
BGP and PCEP configurations to take advantage of it. Since the runtime
support is not universally available, these options are left
deactivated.

Change-Id: I61d455966aada9e0cc68dadab724994ba8dcb794
Signed-off-by: Robert Varga <rovarga@cisco.com>