Fix incompatibility with latest graphviz svg format

Change-Id: I8a0f0d31166e273384de6809ba2a784bcf079903
Reviewed-on: https://gerrit.spotify.net/gerrit/45144
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Erik Bernhardsson <erikbern@spotify.com>