We don't need to parse out the counter values from the iptables-save
output (since they are always 0 for the chains we care about). Just
parse the chain names themselves.
Also, all of the callers of GetChainLines() pass it input that
contains only a single table, so just assume that, rather than
carefully parsing only a single table's worth of the input.
The test was calling GetChainLines() on invalid pseudo-iptables-save
output where most of the lines were indented. GetChainLines() happened
to still parse this "correctly", but it would be better to be testing
it on actually-correct data.
