audioflinger_fuzzer : Avoid configuration of invalid values

This update avoids configuring of invalid values which lead to abort

Test: ./audioflinger_fuzzer -rss_limit_mb=2560 -timeout=90 -runs=100
      clusterfuzz-testcase-minimized-audioflinger_fuzzer-5701813725167616
Bug: 180357329

Change-Id: Iedc5d35e3f0c445c6e9278292462e0edf6c022f0
(cherry picked from commit 95b1327f7d6b0ff127960dd6012414ea1e8f8169)