Now, we set 'fixed_ips' to [] for server ports when prepare
for server replacement, but the ports are still in-use if only
set 'fixed_ips' to []. So this patch will to detach the ports from
nova server to make sure same ports can be attached to new one in
prepare_for_replace(). Also, when restoring server, we need to detach
ports from existing server, and then to attach them to previous
server.
We check the interface attach/detach complete by list the
server.interfaces, this change will use 'retry' wrapper to re-poll
the server interfaces for several times (by new config option
'max_interface_check_attempts', default is 10), then will raise
exception if the attach/detach still not complete.
Closes-Bug: #1533076
Change-Id: I7b322f9cf16c100dcd0365bc3091c289f00f0548
163d46bdc8