Removed RWLock fuzzer

The class being fuzzed here was too simple for a fuzzer to be effective at finding crashes that were not working as intended.
To resolve the issue noted in 163775285 would require the fuzzer to simply use RWLock exactly as intended, defeating the point of fuzzing it.
Because of this, we have made the decision to remove this class. It should have a fairly small impact on coverage. In the future,
perhaps a better approach would be fuzzing pthread's rwlock methods directly.
Test: Made sure the project still builds without RWLock_fuzz.

Signed-off-by: Dylan Katz <dylan.katz@leviathansecurity.com>
Change-Id: Id5e77d053dc800a982176802dc506d26b54d810f