Update kubernetes-network-encryption.md
Update kubernetes-network-encryption.md

Added MTU instruction per @ctelfer
thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io