remove product_data, protocol_data parameters from try_dissect_next_protocol()
(another small step to make this function understandable)

Change-Id: Ib00aa00af8287969dd2d80a33c1f0ebd0b8f2248
Reviewed-on: https://code.wireshark.org/review/3734
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Martin Kaiser <wireshark@kaiser.cx>