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

hgext/lfs/blobstore.py

@@ -110,11 +110,12 b' class lfsuploadfile(object):'
     def read(self, size):
         if self._fp is None:
             return b''
-        data = self._fp.read(size)
-        if not data:
+        return self._fp.read(size)
+
+    def close(self):
+        if self._fp is not None:
             self._fp.close()
             self._fp = None
-        return data
 
 
 class local(object):
@@ -539,6 +540,9 b' class _gitlfsremote(object):'
             raise LfsRemoteError(
                 _(b'LFS error: %s') % _urlerrorreason(ex), hint=hint
             )
+        finally:
+            if request.data:
+                request.data.close()
 
     def _batch(self, pointers, localstore, action):
         if action not in [b'upload', b'download']: