[libvirt] [PATCHv3 0/4] util: fix libvirtd startup failure due to netlink error

The initial patch in this series is the same as the single patch I provided before, but in addition there are 3 new patches that take care of the fallout from 1/4 by: 2/4) removing hard-coding of the src nl_pid when virNetLinkCommand is sending a message 3/4) adding a helper function to retrieve the local nl_pid from a libnl socket and 4/4) using that value when appropriate (I think). As before, I'm unable to fully test this myself, so I won't push unless/until I get verification it works.