Don't try bypass_1691487 for graphical base_selinux runs

This just doesn't work when running the test on a graphical
install because we're at a desktop when we try and do it, not
a text console. So let's only try to do it if there is no
DESKTOP. See e.g.:

https://openqa.fedoraproject.org/tests/408484#step/base_selinux/2

Signed-off-by: Adam Williamson <awilliam@redhat.com>

tests/base_selinux.pm

@@ -5,7 +5,7 @@ use utils;
 
 sub run {
     my $self=shift;
-    bypass_1691487;
+    bypass_1691487 unless (get_var("DESKTOP"));
     # switch to TTY3 for both, graphical and console tests
     $self->root_console(tty=>3);
     validate_script_output 'getenforce', sub { $_ =~ m/Enforcing/ };