Enable seccomp in init with generated policy

Test: Ran script to test performance - https://b.corp.google.com/issues/32313202#comment3
      Saw no significant regression with this change on or off
      Removed chroot from SYSCALLS.TXT - chroot blocked
      Boot time appears reasonable
      Device boots with no SECCOMP blockings
      Measured per syscall time of 100ns
      Empirically counted <100,000 syscalls a second under heavy load

Bug: 32313202
Change-Id: Icfcfbcb72b2de1b38f1ad6a82e8ece3bd1c9e7ec