[issue18819] tarfile fills devmajor and devminor fields even for non-devices

[Ned Deily]

Change by Ned Deily <nad at python.org>:


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nosy: +ethan.furman
versions:  -Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue18819>
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