cifs: update the default global_secflags to include "raw" NTLMv2

Before this patchset, the global_secflags could only offer up a single
sectype. With the new set though we have the ability to allow different
sectypes since we sort out the one to use after talking to the server.

Change the global_secflags to allow NTLMSSP or NTLMv2 by default. If the
server sets the extended security bit in the Negotiate response, then
we'll use NTLMSSP. If it doesn't then we'll use raw NTLMv2. Mounting a
LANMAN server will still require a sec= option by default.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>