Fix fuzzer testcase

Fuzzer reports show memory leaks emanating from fuzz_alarm.cc.
On investigation these are invalid and stem from problems with
memory and flow management in the fuzzer implementation.

Fix those issues.

Bug: 262875478
Test: fuzz
Tag: #security
Ignore-AOSP-First: Security
Change-Id: I3db039f3841bb19be52957fdb968ff09c9327e7f