mutator: fix a rare test case

The rare case happens for proto float/double fields that are
initiated with -0.0/-0.0f; detached to 0.0/0.0f; and mutated back to
-0.0/-0.0f. This previously caused a rare random failure of the StressTest.java.

src/test/java/com/code_intelligence/jazzer/mutation/mutator/StressTest.java

@@ -456,6 +456,7 @@ void genericMutatorStressTest(AnnotatedType type, String mutatorTree,
       testReadWriteExclusiveRoundtrip(mutator, fixedValue);
 
       initValues.add(mutator.detach(value));
+      value = fixFloatingPointsForProtos(value);
 
       for (int mutation = 0; mutation < NUM_MUTATE_PER_INIT; mutation++) {
         Object detachedOldValue = mutator.detach(value);