Add a fuzzer for system_properties.

This could be improved by testing private functions like read_raw or
by improving wait fuzzing so that it will fuzz things it cannot write,
but those seem like little enough gain for more work, so we'll start
with this.

Test: Run fuzzer.
Change-Id: I4c5a04fd3e18a5c975a0e000fbae1a236699192d
2 files changed