protodetect: opposing side cannot change protocol

protodetect: opposing side cannot change protocol

Ticket: #4562

As the data which triggered the opposing side
was the same protocol and not another one,
that means the protocol change failed.

Prevents a memory leak in later call of AppLayerParserParse
which would allocate a new state and leak the old one

(cherry picked from commit be617a3c1b25a7a4b1acdc7b65d3733d4f48a1f9)