Separate child process sync from user namespace

Syncing the child and parent was only done so that the uid/gid maps
could be setup.  Make this more general so that the next commit can add setting
of cgroups which also wants to happen after the child forks but before the
jailed process is run similar top uid/gid map setting.

BUG=b/26549867
TEST=security_Minijail0

Change-Id: I81d512f351cfe459cd7af4c55263504d22b929fa
Signed-off-by: Dylan Reid <dgreid@chromium.org>
1 file changed