fix installedtest post-fail hook when no /var/tmp/abrt

Summary:
you can't use validate_script_output like this, it doesn't just
return a bool, it actually kills the test if the output doesn't
validate. So any time we didn't have anything in /var/tmp/abrt,
the post_fail_hook would die at that point and not upload the
contents of /var/log as we wanted it to.

Note that even script_output will kill the test if the return
code is >0. That's OK in this case, but always be careful with
these subroutines.

Test Plan:
Run a test that fails in post-install but doesn't
produce anything in /var/tmp/abrt (you may have to artificially
break something). Check that it now uploads /var/log. I noticed
this while working on FreeIPA tests...

Reviewers: jskladan, garretraziel

Reviewed By: garretraziel

Subscribers: tflink

Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D830

lib/installedtest.pm

@@ -25,7 +25,8 @@ sub post_fail_hook {
     $self->root_console(tty=>2);
 
     # If /var/tmp/abrt directory isn't empty (ls doesn't return empty string)
-    if (validate_script_output "ls /var/tmp/abrt", sub { $_ ne '' }) {
+    my $vartmp = script_output "ls /var/tmp/abrt";
+    if ($vartmp ne '') {
         # Upload all ABRT logs
         script_run "cd /var/tmp/abrt && tar czvf abrt.tar.gz *";
         upload_logs "/var/tmp/abrt/abrt.tar.gz";