9P/SELinux: fixes bug when managing flags EXPORT_OPTION_SELINUX

Change-Id: Ia150c9288b4f2bca6019f0147a401a958bd9952c
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
9P/SELinux: _9p_check_security() returns EACCES when SELinux is disabled.

Change-Id: I0be08c9bc70047afb59f7e219b6b6c007c43c658
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>