api: fix file cleanup edge case

Processes could still be spawned writing files after the app has cleaned the dir out, and is ready to clear it out.
Dumb edge case, but oh well.

api/src/job.js

@@ -280,10 +280,8 @@ class Job {
     async cleanup() {
         logger.info(`Cleaning up job uuid=${this.uuid}`);
 
-        await Promise.all([
-            this.cleanup_processes(),
-            this.cleanup_filesystem(),
-        ]);
+        await this.cleanup_processes();
+        await this.cleanup_filesystem();
     }
 }