Manual testing protocol:
* Verify prng_seeder daemon is running and has the
correct label (via ps -Z)
* Verify prng_seeder socket present and has correct
label (via ls -Z)
* Verify no SELinux denials
* strace a libcrypto process and verify it reads seeding
data from prng_seeder (e.g. strace bssl rand -hex 1024)
* strace seeder daemon to observe incoming connections
(e.g. strace -f -p `pgrep prng_seeder`)
* Kill daemon, observe that init restarts it
* strace again and observe clients now seed from new instance
Bug: 243933553
Test: Manual - see above
Change-Id: I0a7e339115a2cf6b819730dcf5f8b189a339c57d
