Fixing improper boxing to Integer instead of Long.

This is tricky: entry.getMessageBox() returns int, so it is
by default boxed to Integer. Map.get() however accepts Objects,
so it ignores the difference, but nothing is find during lookup,
just because Long and Integer objects are compared using equals(),
which has to lead to 'false' result. So, explicit boxning to Long
is unnecessary here.

Change-Id: I967a7829a8926410a00274c6b5e312e1af567299