Revert "Fix pread logic"

This reverts commit 96c462e5f639044439ec8ffb4f65f7d96153b7d7.
diff --git a/src/couch/src/couch_file.erl b/src/couch/src/couch_file.erl
index e7fd229..0cfc91e 100644
--- a/src/couch/src/couch_file.erl
+++ b/src/couch/src/couch_file.erl
@@ -199,9 +199,7 @@
     {ok, iolist_to_binary(L)}.
 
 
-pread_iolist(#ioq_file{parallel=true, fd=Fd}, Pos) ->
-    Limit = get_pread_limit(),
-    File = #file{fd=Fd, is_sys=false, pread_limit=Limit},
+pread_iolist(#ioq_file{parallel=true, fd=File}, Pos) ->
     {LenIolist, NextPos} = read_raw_iolist_int(File, Pos, 4),
     case iolist_to_binary(LenIolist) of
         <<1:1/integer,Len:31/integer>> -> % an MD5-prefixed term