Support network_device_mtu of nova managed interfaces

network_device_mtu configure the MTU for nova managed network interfaces.
By default no specific network_device_mtu configuration is set. The
interface defaults will be used as they got created.

This options allows configuration of Jumbo Frame usage.

Change-Id: Ia391f3daa788c780c4492071a480052b4ef4cc37
Fix vncproxy package/service name on Debian

This commit fix vncproxy on debian os, we have now a duplicate
between nova::vncproxy and nova::spicehtml5proxy packages on debian
but install both have no sense…

Closes-bug: #1267645

Change-Id: Ib0a769ba91221d1ebc14df01f24579c8fe58db26
Merge "Fix vncproxy package/service name on Debian"
Merge "Support network_device_mtu of nova managed interfaces"