Add dbus signal for information about server certification

Add dbus signal for information about server certification

In general, this patch attemps to extend commit
00468b4650998144f794762206c695c962c54734 with dbus support.

This can be used by dbus client to implement subject match text
entry with preset value probed from server. This preset value, if
user accepts it, is remembered and passed to subject_match config
for any future authentication.

Signed-off-by: Michael Chang <mchang@novell.com>