libfakeservicemanager: thread safe

Wasn't, used in fuzzers in a way that is hard
to prove whether it's really needed or not.
Avoid possibly hard to diagnose future issues.

Bug: N/A
Test: libfakeservicemanager_test
Change-Id: I91d4d769ce40c1c3b82fb64fff748a380b43b8b6
2 files changed