flua: fbsd: avoid leaking stdin pipes on error

[kevans]

Summary

Additionally, there's no way to get to the end without a valid
stdin_pipe[1] at the moment, so don't check for it. stdin_pipe[0] is
closed earlier, as the parent shouldn't need the read-side of the pipe.

While we're here, also free the file actions earlier -- they're not
necessary once posix_spawn() has returned.

[markj]

libexec/flua/modules/lfbsd.c

100

I think we need to destroy file actions if posix_spawnp() fails too.

[bapt]

@markj is right there about the actions