build: -avoid-version on libvirt_driver_nwfilter
build: -avoid-version on libvirt_driver_nwfilter

This fixes the following make rpm warning:

warning: Installed (but unpackaged) file(s) found:
   /usr/lib64/libvirt/connection-driver/libvirt_driver_nwfilter.so.0
   /usr/lib64/libvirt/connection-driver/libvirt_driver_nwfilter.so.0.0.0

introduced in comit 8d559864

Signed-off-by: Dwight Engen <1793d65cf7b9eefb2bb8f5bee9a4b8ba782c26da@oracle.com>
Signed-off-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

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