[v1alpha2] Potential bugs when there is one worker succeeded

[gaocegege]

Test Case:

"Distributed TFJob (4 workers, 2 PS) is created, 2 workers, 1 PS are pending, 1 worker is succeeded": {
			4, 2,
			nil, true,
			2, 0, 1, 0,
			1, 0, 0, 0,
			3, 1,
			1, 0, 1,
			3, 0, 0,
			2, 0, 0,
			&tfJobRunning, tfJobRunningReason,
			false,
		},

[jlewi]

Its not clear to me from the issue description what the expected outcome is and what the actual outcome is.

[gaocegege]

The description is we expect not to create new pods for the succeeded workers but we do create now.

[gaocegege]

Close in #548