Machine status: Don't show removed machines anymore

This requires a sequential scan on the BuildSteps table, which by now
takes > 8s.

src/lib/Hydra/Controller/Root.pm

@@ -75,12 +75,18 @@ sub status :Local {
 sub machines :Local Args(0) {
     my ($self, $c) = @_;
     my $machines = getMachines;
-    my $idles = $c->model('DB::BuildSteps')->search(
-            { stoptime => { '!=', undef } },
-            { select => [ 'machine', { max => 'stoptime', -as => 'max_stoptime' }], group_by => "machine" });
-    while (my $idle = $idles->next) {
-        ${$machines}{$idle->machine}{'idle'} = $idle->get_column('max_stoptime');
+
+    # Add entry for localhost.
+    ${$machines}{''} //= {};
+
+    # Get the last finished build step for each machine.
+    foreach my $m (keys %{$machines}) {
+        my $idle = $c->model('DB::BuildSteps')->find(
+            { machine => "$m", stoptime => { '!=', undef } },
+            { order_by => 'stoptime desc', rows => 1 });
+        ${$machines}{$m}{'idle'} = $idle ? $idle->stoptime : 0;
     }
+    
     $c->stash->{machines} = $machines;
     $c->stash->{steps} = [ $c->model('DB::BuildSteps')->search(
         { finished => 0, 'me.busy' => 1, 'build.busy' => 1, },

src/root/machine-status.tt

@@ -7,11 +7,7 @@
     <thead>
       <tr>
         <th colspan="5">
-          [% IF !m.key || m.value.maxJobs %]
-            Enabled:
-          [% ELSE %]
-            Disabled:
-          [% END %] <tt>[% name %]</tt>
+          <tt>[% name %]</tt>
           [% IF m.value.systemTypes %]
             ([% comma=0; FOREACH system IN m.value.systemTypes %][% IF comma; %], [% ELSE; comma = 1; END %]<tt>[% system %]</tt>[% END %])
           [% END %]
@@ -35,7 +31,7 @@
       [% END %]
       [% IF idle == 1 %]
         [% IF m.value.idle %] 
-          <tr><td colspan="5">Idle since [% INCLUDE renderDuration duration = curTime - m.value.idle %]</td></tr>
+          <tr><td colspan="5">Idle for [% INCLUDE renderDuration duration = curTime - m.value.idle %]</td></tr>
         [% ELSE %]
           <tr><td colspan="5">Never used</td></tr>
         [% END %]