tlscontext: Make hostname check in tls certificate case insensitive
tlscontext: do not accept certificate which is not contained by the list of fingerprints

Signed-off-by: Juhász Viktor <jviktor@balabit.hu>
Signed-off-by: Budai Laszlo <Laszlo.Budai@balabit.com>
Merge pull request #293 from lbudai/3.6/tlscontext-fix

3.6/tlscontext fix