Wrap eventlet's Timeout exception

Eventlet's Timeout was subclass of Exception. But at some point it
switched to BaseException. Now statements like

  except Exception as e:

do not catch it. Wrapping Timeout into our own one fixes this.

Change-Id: I90bf3b2335359e1f7f4c376e0e7292f18c75f162
Merge "Wrap eventlet's Timeout exception"