Fix add-fixed-ip and remove-fixed-ip.

There were various places that were passing an integer id from
network api to network manager. On the manager side we need the
uuid so this patch updates everything to send the uuid.

Secondarily, the network info cache wasn't being properly updated
upon return from add-fixed-ip and remove-fixed-ip, so this
changes the code to update the info cache as well.

Fixes bug 1124674

Change-Id: I632b39eb3963998cf42c02584dc9275a8aae243d
Only dhcp the first ip for each mac address.

When using add-fixed-ip there can be more than one ip for each
mac so make dnsmasq just serve the first one. Also, make sure to
disassociate the fixed ips when they are removed since dnsmasq
will never know about them.

Fixes bug 1124692

Change-Id: If41c03e1adb408ce28d8e8a25706ebc76fb3c4e1