ASN.1 dissectors - don't try to find yourself.

ASN.1 dissectors - don't try to find yourself.

If an ASN.1 dissector is calling register_dissector for itself in its proto_register_xxx
function and then calling find_dissector for itself in its proto_reg_handoff_xxx
function then just create a static handle for that dissector and use the return
value of register_dissector, so the find isn't necessary.

Change-Id: I911bdadc2fb4259601c141b955e741a2369cc447
Reviewed-on: https://code.wireshark.org/review/16233
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>