.arcconfig

lfs: explicitly close the file handle for the blob being uploaded

The previous code relied on reading the blob fully to close it.  The obvious
problem is if an error occurs before that point.  But there is also a problem
when using workers where the data may need to be re-read, which can't happen
once it is closed.  This eliminates the surprising behavior before attempting to
fix the worker problem.

Differential Revision: https://phab.mercurial-scm.org/D7957

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