RootCanal: Prevent abort on unknown APCF opcode

Gracefullly handle the unknown opcode by returning
an error status code, and reporting the command
to the invalid packet handler.

Bug: 323226412
Flag: EXEMPT, tool change
Test: m root-canal
Change-Id: I446d1f2bc51ac3161ad645c3e6e5ed469f04b2f8