Switch to using eventlet_backdoor from oslo.
Switch to using eventlet_backdoor from oslo.

Instead of using the copy of eventlet_backdoor in nova.common
this switches over to the synced version from oslo.

Change-Id: Ice2e38b9da66b34e19f04af0a99bcdc2cb5b5cd3
Signed-off-by: Matthew Treinish <17bfc8751a60276d19cd7f0cbe3763e22d3e07a0@linux.vnet.ibm.com>

n0ano/ganttclient