Merging r354402:

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r354402 | eugenis | 2019-02-20 00:41:42 +0100 (Wed, 20 Feb 2019) | 3 lines

[msan] Fix name_to_handle_at test on overlayfs.

Udev supports name_to_handle_at. Use /dev/null instead of /bin/cat.
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llvm-svn: 354460