Lua accessor for Protocol field type gets wrong data

When a Lua dissector/tap accesses the value of a Field of FT_PROTOCOL ftype, the
returned ByteArray contains the wrong data.  Also, calling such a field's
tostring() method returns a string of "(unknown)" instead of the hex of the
data.

Bug: 10801
Change-Id: I8a0642dc0e41af444d211bbe4106cd21207084a6
Reviewed-on: https://code.wireshark.org/review/6003
Reviewed-on: https://code.wireshark.org/review/6133
Petri-Dish: Hadriel Kaplan <hadrielk@yahoo.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>