docs: fix memballoon examples
docs: fix memballoon examples

Use a pair of 'memballoon' tags instead of single 'watchdog' one.
Add a few missing colons.

agx/libvirt,cbosdo/libvirt,datto/libvirt,rlaager/libvirt,nertpinx/libvirt,rlaager/libvirt,eskultety/libvirt,andreabolognani/libvirt,agx/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,taget/libvirt,nertpinx/libvirt,datto/libvirt,rlaager/libvirt,agx/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt,VenkatDatta/libvirt,zippy2/libvirt,taget/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,jardasgit/libvirt,cbosdo/libvirt,zippy2/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,olafhering/libvirt,eskultety/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,jardasgit/libvirt,datto/libvirt,fabianfreyer/libvirt,agx/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,cbosdo/libvirt,cbosdo/libvirt,andreabolognani/libvirt,crobinso/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,datto/libvirt,VenkatDatta/libvirt,taget/libvirt,VenkatDatta/libvirt,crobinso/libvirt,libvirt/libvirt,elmarco/libvirt,crobinso/libvirt,rlaager/libvirt,elmarco/libvirt,jfehlig/libvirt,nertpinx/libvirt,zhlcindy/libvirt-1.1.4-maintain,nertpinx/libvirt,zhlcindy/libvirt-1.1.4-maintain,olafhering/libvirt,andreabolognani/libvirt,agx/libvirt,taget/libvirt,zippy2/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,elmarco/libvirt,shugaoye/libvirt,taget/libvirt,eskultety/libvirt,jfehlig/libvirt,crobinso/libvirt,eskultety/libvirt,jardasgit/libvirt,cbosdo/libvirt,shugaoye/libvirt,datto/libvirt,andreabolognani/libvirt,shugaoye/libvirt,jardasgit/libvirt,shugaoye/libvirt,jfehlig/libvirt,elmarco/libvirt,libvirt/libvirt,elmarco/libvirt,shugaoye/libvirt