tests, network: correct the string length
tests, network: correct the string length

The length of the "Hello world!" string is 12, not 11.

Signed-off-by: Miguel Duarte Barroso <c798d3f0e4fda7badfc3bbd91babde7ebd48b6c2@redhat.com>

kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt