Add missing error log statements.

When "markRunnerAsUsed" fails, we silently ignored it. Only, when additionally the return of the runner failed, we threw the error.

When a Runner is destroyed, we are only notified that Nomad removed the allocation, but cannot tell about the reason.

For "the execution did not stop after SIGQUIT" we did not log the belonging runner id.

internal/runner/nomad_manager.go

@@ -62,6 +62,7 @@ func (m *NomadRunnerManager) markRunnerAsUsed(runner Runner, timeoutDuration int
 		return
 	})
 	if err != nil {
+		log.WithError(err).WithField(dto.KeyRunnerID, runner.ID()).Error("cannot mark runner as used")
 		err := m.Return(runner)
 		if err != nil {
 			log.WithError(err).WithField(dto.KeyRunnerID, runner.ID()).Error("can't mark runner as used and can't return runner")