Remove flcache entries if the connection is prematurely closed from the client side.

Fix issue #1124

Signed-off-by: Mathias Kunert <mathias.kunert@dezem.de>
Merge pull request #1128 from mathkn/fix_flcache_incomplete_files

Remove flcache entries if the connection is prematurely closed from the ...
Apply the patch from @kinnison to fix #1121 thanks DalekSec for pursuing.