flask: check permissions first thing in flask_security_set_bool()

Nothing else should be done if the caller isn't permitted to set
boolean values.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/xsm/flask/flask_op.c
+++ b/xen/xsm/flask/flask_op.c
@@ -326,11 +326,11 @@ static int flask_security_set_bool(struc
 {
     int rv;
 
-    rv = flask_security_resolve_bool(arg);
+    rv = domain_has_security(current->domain, SECURITY__SETBOOL);
     if ( rv )
         return rv;
 
-    rv = domain_has_security(current->domain, SECURITY__SETBOOL);
+    rv = flask_security_resolve_bool(arg);
     if ( rv )
         return rv;