Update travis-ci to work with Varnish 4.0.
Update travis-ci to work with Varnish 4.0.

mbgrydeland/libvmod-fsbackend,Dridi/libvmod-example,mbgrydeland/libvmod-fsbackend,varnish/libvmod-example,aondio/libvmod-rtfrontend,aondio/libvmod-cowsay,aondio/libvmod-cowsay,Dridi/libvmod-example,varnish/libvmod-example,aondio/libvmod-rtfrontend,aondio/libvmod-rtfrontend