Android seccomp-bpf: allow clone without CLONE_DETACHED

sandbox_linux_unittests has a test that keeps track on the clone() flags
that can be used by the C library. Recent Android versions don't use the
deprecated CLONE_DETACHED anymore.

BUG=302042
R=palmer@chromium.org

Review URL: https://codereview.chromium.org/25364003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226101 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226101