Don't abort, return nullptr instead, when config file isn't present

Reduce the number of calls to CuttlefishConfig::Get(): We have been
abusing the singleton, which made it hard to keep track of what
happens before and after config is initialized in the launcher.

Bug: 111084325
Test: local & gce
Change-Id: I513eccacb221695fd046551d54bb8b98f7348ea8
15 files changed
tree: 733f8db5543d4f04cbee041f550bccd1185c215f
  1. common/
  2. guest/
  3. host/
  4. tests/
  5. tools/
  6. Android.bp
  7. Android.mk
  8. OWNERS