qemuBuildHostNetStr: Explicitly enumerate net types
qemuBuildHostNetStr: Explicitly enumerate net types

We tend to prevent using 'default' in switches. And it is for a
good reason - control may end up in paths we wouldn't want for
new values. In this specific case, if qemuBuildHostNetStr is
called over VIR_DOMAIN_NET_TYPE_VHOSTUSER it would produce
meaningless output. Fortunately, there no such call yet.

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

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