Make src/test/test-network.sh and friends handle out-of-tree builds

Make src/test/test-network.sh handle out-of-tree builds by removing the assumption that we will always be in the tor directory when building.

Add code to src/test/test-network.sh like:

TOR_PATH="`dirname $0`/../or/tor"

A similar change was made to src/test/zero_length_keys.sh in legacy/trac#13111 (moved).

Review other scripts to see if they have the same issue.