Errors in updateGitlabCommitStatus do not appear in build log due to null TaskListener

### Context
- **Gitlab plugin version**: 1.4.8
- **Gitlab version**: 10.1.0
- **Jenkins version**: 2.60.3
- **Job type**: Pipeline (declarative)

### Problem description

If an error occurs in an `updateGitlabCommitStatus` pipeline step inside the call to `CommitStatusUpdater.updateCommitStatus`, then the log messages do not appear in the build's log due to the step implementation passing a null `TaskListener` argument. This means that the message ends up in the Jenkins system log instead as `failed to print message $ACTUAL_MESSAGE due to null TaskListener`, leaving the user confused as to why the commit status update failed in their build until they can contact an admin user who can look at the system log.