test: Add TLS tracking integration test

This patch adds a new test, which verifies the TLS tracking.

Because we need to simulate SPF records, and Go does not support fully
intercepting DNS lookups yet, this test relies on dnsmasq to provide a
DNS resolver.

In the future, once Go supports DNS lookup interception, we can get rid
of this additional dependency.

test/cover.sh

@@ -42,6 +42,8 @@ go run "${UTILDIR}/gocovcat.go" .coverage/*.out \
 go tool cover -func="$COVER_DIR/all.out" | sort -k 3 -n > "$COVER_DIR/func.txt"
 go tool cover -html="$COVER_DIR/all.out" -o "$COVER_DIR/chasquid.html"
 
+echo
+grep total .coverage/func.txt
 echo
 echo "Coverage report can be found in:"
 echo file://$COVER_DIR/chasquid.html