Fix bug in processing jobs on platforms without Docker (#1834)

* Log incoming jobs.

Log the full contents of the job protobuf to make debugging jobs easier

* Ensure that the parallel executor always uses at least one thread.

The caller may mis-calculate the number of CPUs as zero, in which case
ensure that at least one thread is spawned.

* Use runtime.NumCPU for CPU counts.

For hosts without docker, GetHostInfo() returns a blank struct which
has zero CPUs and causes downstream trouble.

---------

Co-authored-by: Paul Armstrong <psa@users.noreply.gitea.com>
Co-authored-by: Jason Song <i@wolfogre.com>

pkg/model/workflow.go

@@ -417,6 +417,7 @@ func (j *Job) GetMatrixes() ([]map[string]interface{}, error) {
 		}
 	} else {
 		matrixes = append(matrixes, make(map[string]interface{}))
+		log.Debugf("Empty Strategy, matrixes=%v", matrixes)
 	}
 	return matrixes, nil
 }