netd: Make tests/runtest.sh use Soong

Also:
 - Add netdutils_test
 - Enable 'set -e' (exit on errors)
 - Enable 'set -u' (exit on undefined variable expansion)
 - Count skipped tests

Test: run tests/runtests.sh
Change-Id: I335be3751d0e18b19c76dd8bf054b7547a49bb71