audiopolicy: Remove global static initializers

Replace global static instances of non-primitive
types with function static instances. The latter
get initialized on the first call to the function
instead of module load time.

This also gets rid of ASAN UAF errors reported
during unit test execution.

Bug: 150649241
Test: atest audiopolicy_tests
Test: atest audio_health_tests
  (for ASAN-instrumented libraries and test)
Change-Id: I514c9205b9d3e7a3f0a1d8aa71d71fcc792e7a7b
Merged-In: I514c9205b9d3e7a3f0a1d8aa71d71fcc792e7a7b