cifs: set MAY_SIGN when sec=krb5

Setting this secFlg allows usage of dfs where some servers require
signing and others don't.
Signed-off-by: Martijn de Gouw <martijn.de.gouw@prodrive.nl>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/connect.c

@@ -1031,7 +1031,7 @@ static int cifs_parse_security_flavors(char *value,
 
 	switch (match_token(value, cifs_secflavor_tokens, args)) {
 	case Opt_sec_krb5:
-		vol->secFlg |= CIFSSEC_MAY_KRB5;
+		vol->secFlg |= CIFSSEC_MAY_KRB5 | CIFSSEC_MAY_SIGN;
 		break;
 	case Opt_sec_krb5i:
 		vol->secFlg |= CIFSSEC_MAY_KRB5 | CIFSSEC_MUST_SIGN;