Predictable iptables chains output order

Predictable iptables chains output order

This fixes the iptables unit tests that break with a randomized PYTHONHASHSEED
(see the bug report).

The chains for iptables are stored as sets to avoid duplicates. When they are
output by iptables_manager their order can therefore be unpredictable. This was
found hash seed 1016732220.

To fix this we:
 - Sort the chains output by iptables_manager
 - Update the unit tests to check for sorted chains

When multiple tables are processed, they can be processed in any order or
dumped in any order. Found with hash seed 3728666619.

To fix this we:
 - Traverse the tables in sorted order for dumping
 - Fix tests to allow for tables to be processed in any order

Note: There are several other unrelated unit tests that also break with a
randomized PYTHONHASHSEED, but they are not addressed here. They will be
addressed in separate patches.

Partial-bug: #1348818

Change-Id: Ic3f4cd85316c9fc2e78bc7f5e900cfac87baf39d