[CLATJ#28] ClatCoordinator: spawn clatd with flag POSIX_SPAWN_CLOEXEC_DEFAULT

Close the leaking fds before spawning a process. The leaking fds
are unused by clatd and they cause unexpected avc denials. Close
the unused fds before clatd forked.

Bug: 230071136
Bug: 212345928
Test: atest FrameworksNetTests
      manual test
      1. Connect to ipv6-only wifi.
      2. Try IPv4 traffic.
         $ ping 8.8.8.8

Change-Id: I4f095cccd999b7dfd7fe87032bf7de81a925a4da
1 file changed