Only post to coveralls if we have a coveralls token setup

[Larusso]

Some pipelines fail if we don't have a coveralls token setup.
In these cases we should not send the POST messages.

atlas-jenkins-pipeline/vars/buildJavaLibraryOSSRH.groovy

Line 118 in ee69269

httpRequest httpMode: 'POST', ignoreSslErrors: true, url: "https://coveralls.io/webhook?repo_token=${config.coverallsToken}"