title: psutil.process_iter() doesn't return all running processes
body: <p>I'm using psutil 2.1.2 on python 64 bit on windows 8.1. I'm using psutil.process_iter() to iterate over the running processes to get details on a specific process. for some reason I don't get the process even though it is displayed in the Task Manager and the Process Explorer</p>
  
  <pre><code>for proc in psutil.process_iter():
      try:
          if proc.name() == 'svchost.exe':  # patch for debugging 
              pass  #script never gets here
          opened_files = proc.open_files()
          opened_files = [opened_file[0] for opened_file in opened_files]
          if file_path in opened_files:
              processes.append(proc)
      except (psutil.AccessDenied, psutil.NoSuchProcess):
          pass
  </code></pre>
  
  <p>I checked the proc name and it is never the process I'm looking for.
  example of a process I don't see is svchost.exe</p>
  
  <p>Thanks for the help!</p>