Fixed a bug that ACK fails to produce local devices list.
when xensource_inventory has an entry of PRIMARY_DISK, a real path.
Merge pull request #54 from bpwook/localstorage

Fixed a bug that ACK fails to produce local devices list
Now ACK changes network backend for both of master and slave.
When ACK changes network backend it only changes master. It is not fit with use-case. Now it changes backend both master and slave when it is directed to do so.
Merge pull request #55 from bpwook/netback

Now ACK changes network backend for both of master and slave.