Fix interface-list got none mac address.

novaclient expect the response json body has a column 'mac_address', but
actually is 'mac_addr'. This patch is a quick fix. Just print out
"mac_addr" is readable enough.

Fix bug: #1199706

Change-Id: I68823a3d719ee2f5d9d8b6227ca8eb858fc270c3
Merge "Fix interface-list got none mac address."