kex, pki, server, options: Filter algorithms in FIPS mode

When in FIPS mode, filter the algorithms to enable only the allowed
ones. If any algorithm is explicitly set through options or
configuration file, they are kept.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>