Attach/detach interface to paused instance with affect live flag

Currently attach/detach interface to paused instance is only with
VIR_DOMAIN_AFFECT_CONFIG flags. After instance unpause, there isn't
any effect on the instance, unless restart the instance. So add
flag VIR_DOMAIN_AFFECT_LIVE when attach/detach interface.

Conflicts:
	nova/tests/virt/libvirt/test_libvirt.py

Change-Id: Iedfc7f6fc06e72d8e3eecebede1274582c8043fd
Closes-Bug: #1299331
(cherry picked from commit a868fcedf8e46070cae6aa8e59e61934fa23db1c)
Merge "Attach/detach interface to paused instance with affect live flag" into stable/icehouse