qemuAgentGetInterfaces: Don't error out on missing HW address
qemuAgentGetInterfaces: Don't error out on missing HW address

Now that we allow HW address to be not present on our RPC layer,
don't error out if qemu-ga hasn't provided any.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

nertpinx/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,zippy2/libvirt,taget/libvirt,olafhering/libvirt,olafhering/libvirt,jardasgit/libvirt,agx/libvirt,crobinso/libvirt,datto/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,datto/libvirt,jardasgit/libvirt,libvirt/libvirt,crobinso/libvirt,agx/libvirt,agx/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,crobinso/libvirt,jardasgit/libvirt,eskultety/libvirt,VenkatDatta/libvirt,zippy2/libvirt,rlaager/libvirt,libvirt/libvirt,jfehlig/libvirt,eskultety/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,rlaager/libvirt,taget/libvirt,andreabolognani/libvirt,eskultety/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,datto/libvirt,fabianfreyer/libvirt,agx/libvirt,olafhering/libvirt,taget/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,jfehlig/libvirt,rlaager/libvirt,eskultety/libvirt,andreabolognani/libvirt,olafhering/libvirt,taget/libvirt,agx/libvirt,VenkatDatta/libvirt,zippy2/libvirt,taget/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,eskultety/libvirt,jardasgit/libvirt,crobinso/libvirt,rlaager/libvirt,datto/libvirt,zippy2/libvirt,rlaager/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,libvirt/libvirt