Description of problem:

* Some VNF requires the use of SRIOV for dataplane interfaces, specifying also a BW for that interface. The BW required for each interface is a requirement specified in the VNF descriptor.
* PCI SRIOV allows multiplexing a single physical interface into several virtual interfaces called Virtual Functions (VF) or SRIOV interfaces. This means that from a single 10G physical interface we should be able to split it in several virtual functions each one consuming a different BW:
    * Example 1: 4 virtual functions with 5Gbps, 2Gbps, 2Gbps and 1Gbps
    * Example 2: 10 virtual functions, each one with 1Gbps
* The number of VF configured in a physical interface can be high, for instance 64, but the number of actually used VF in a physical interface depends on the actual BW reserved for each VF and the total BW of the physical interface.
* When searching a host to deploy a VM, nova scheduler should take into account the amount of BW reserved by the previous VMs on each physical interface. Today, BW is not taken into consideration.
* Moreover, BW occupied on each physical interface is an important driver for host selection. It might make sense for nova to have some policy that prefers deploying on a host whose physical interfaces have less available BW in order to make a better use of the network resources.