Windows clients forget GSS_C_MUTUAL_FLAG in some situations where they
use GSS_C_DCE_STYLE, in the assumption that GSS_C_MUTUAL_FLAG is
implied.
Both Windows and MIT as server already imply GSS_C_MUTUAL_FLAG
when GSS_C_DCE_STYLE is used.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=15740
Signed-off-by: Stefan Metzmacher <metze@samba.org>