upgrade: disable screen blanking before long-running commands

Summary:
Updating the stable release prior to doing the update can take
a long time if the image hasn't been updated for a while, and
the upgrade download process itself can take a long time. If
the screen blanks out in either case, either the following
needle match may fail (if we're waiting for a needle) or 'still
screen' may be detected early (if we're waiting for a still
screen), so let's disable screen blanking to avoid it.

Test Plan: Run the upgrade tests and see if they work.

Reviewers: garretraziel, jskladan

Reviewed By: jskladan

Subscribers: tflink

Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D628

tests/upgrade_preinstall.pm

@@ -13,6 +13,8 @@ sub run {
     }
     # switch to TTY3 for both, graphical and console tests
     $self->root_console(tty=>3);
+    # disable screen blanking (update can take a long time)
+    type_string "setterm -blank 0\n";
 
     # upgrader should be installed on up-to-date system
 

tests/upgrade_run.pm

@@ -11,6 +11,9 @@ sub run {
     if ($release eq 'rawhide' or $milestone eq 'branched') {
         $args .= " --nogpgcheck";
     }
+    # disable screen blanking (download can take a long time)
+    type_string "setterm -blank 0\n";
+
     type_string "dnf -y system-upgrade download ${args}";
     send_key "ret";