Tensorboard logging does not honor `initialEpoch`

[spazmodius]

TensorFlow.js version

2.0.1

Describe the problem or feature request

When training a model, using callback: tf.node.tensorBoard() and initialEpoch: x,
the series graph from step=0, not step=initialEpoch

Code to reproduce the bug / link to feature request

const history = await model.fitDataset(trainData, {
	validationData,
	epochs:100,
	initialEpoch: 23,
	callbacks: tf.node.tensorBoard(tbPath),
})

Probably, this is the source of the issue:
303345f#r41091644

[google-ml-butler]

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