Helper/Nix: constructRunCommandLogPath: take RunCommandLog as input

This way we ensure that it actually exists in the database, rather than
blindly trusting user-generated input.

src/lib/Hydra/Controller/Root.pm

@@ -537,7 +537,8 @@ sub runcommandlog :Local :Args(1) {
 
     die if defined $tail && $tail !~ /^[0-9]+$/;
 
-    my $logFile = constructRunCommandLogPath($uuid);
+    my $runlog = $c->model('DB')->resultset('RunCommandLogs')->find({ uuid => $uuid });
+    my $logFile = constructRunCommandLogPath($runlog);
     if (-f $logFile) {
         serveLogFile($c, $logFile, $tail);
         return;