Created by: egrimley
In check_encode_decode_consistency(), do not try to reencode an OP_UNDECODED instruction.
In instr_encode_arch(), use instr->opcode, not instr_get_opcode(instr), as the latter can call the decoder, which is unhelpful when we are trying to encode.
Fixes #2491
Change-Id: I66c42dc87268f1722eae4600b364026896796fc8