virNetDevOpenvswitchInterfaceStats: Optimize for speed
virNetDevOpenvswitchInterfaceStats: Optimize for speed

We run 'ovs-vsctl' nine times (first to find if interface is
there and then eight times = for each stats member separately).
This is very inefficient. I've found a way to run it once and
with a bit of help from virJSON module we can parse out stats
we need.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

zippy2/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,olafhering/libvirt,andreabolognani/libvirt,jardasgit/libvirt,zippy2/libvirt,jardasgit/libvirt,libvirt/libvirt,olafhering/libvirt,nertpinx/libvirt,nertpinx/libvirt,olafhering/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,crobinso/libvirt,eskultety/libvirt,crobinso/libvirt,libvirt/libvirt,jfehlig/libvirt,crobinso/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,eskultety/libvirt,zippy2/libvirt,eskultety/libvirt,zippy2/libvirt,libvirt/libvirt,olafhering/libvirt,eskultety/libvirt,jardasgit/libvirt,jfehlig/libvirt,andreabolognani/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,nertpinx/libvirt,libvirt/libvirt,crobinso/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt