Previously we had allowed strings to be sent via `note-c` without a newline-terminator.
Subsequently, we decided this was undefined behavior that should not be supported.
This caused a regression in downstream testing, and we have restored the original
behavior (although undefined by the Notecard communication specification).

Allocated string did NOT have a NULL-terminator required by `strstr`.
Fake Function Framework (FFF) does not make copies of strings for testing mocks,
so it was instead accessing released memory which was triggering valgrind errors.