ITS#2465 fix? ber_get_next must read at least sizeof(tag)+sizeof(len)

ITS#2465 fix?  ber_get_next must read at least sizeof(tag)+sizeof(len)
which should be at most 8 bytes. However if we read more than the minimum
message length, we have a problem because we steal bytes from any following
message, and there is no buffer mechanism to push back excess data.
The shortest legitimate message is Unbind at 7 bytes, but there shouldn't
be anything following it. Abandon at 8 bytes is next, so always requesting
at least 8 bytes should be safe. Always requesting 9 was a problem.

Please double-check these assumptions...