Remove error if i doesn't exist, remove useless line

lxc/execute

@@ -18,6 +18,7 @@ basepath="/var/lib/lxc/piston/rootfs"
 exec 200>$dir/lockfile
 flock 200
 
+touch $dir/i
 runner=$(cat $dir/i)
 let 'runner = runner % 150 + 1'
 

shared/execute.js

@@ -37,8 +37,6 @@ function execute(language, source, stdin = '', args = []) {
         });
 
         process.on('exit', code => {
-            unlinkSync(sourceFile);
-
             stderr = stderr.trim().substring(0, OUTPUT_LIMIT);
             stdout = stdout.trim().substring(0, OUTPUT_LIMIT);
             output = output.trim().substring(0, OUTPUT_LIMIT);