Backport test-network.sh fixes to 0.2.9

In our 0.3.4 chutney CI, we get the chutney version of test-network.sh:

test-network.sh: using CHUTNEY_DNS_CONF '/dev/null'
test-network.sh: $TOR_DIR not set, trying $PWD
test-network.sh: $TOR_DIR is a Tor 0.3.4 or earlier build directory

https://travis-ci.org/torproject/tor/jobs/499382754#L3067

But in 0.2.9, we get the tor version of test-network.sh:

test-network.sh: Parsing command-line arguments to find $CHUTNEY_PATH
test-network.sh: $TOR_DIR not set, trying $PWD

Launching chutney using Python 2.7.6

https://travis-ci.org/torproject/tor/jobs/499382330#L2859

But tor 0.2.9's test-network.sh is meant to call chutney's test-network.sh.

We should fix this bug to make sure that we're getting consistent results from our CI. There are a lot of extra bug fixes in the latest chutney's test-network.sh, that aren't in tor 0.2.9's test-network.sh.