Revert "iptables: Change locking semantics."

This reverts commit d2a1e52615058ef55b65db02aa5e4ad21b635ef0.

This is being reverted to minimize diffs with upstream and will
be cherry-picked once upstream is merged.

Bug: 36108349
Test: see top of change stack.
Change-Id: If8136bfd230bf0079884ab94fad0dcdc35a67c47
6 files changed