add make smoke-docker (#287)

This makes it easier to use the docker container smoke test that
GitHub actions runs. There is also `make smoke-docker-race` that runs the
smoke test with `-race` enabled.

.github/workflows/smoke/genconfig.sh

@@ -33,9 +33,9 @@ lighthouse_hosts() {
 
 cat <<EOF
 pki:
-  ca: /ca.crt
-  cert: /${HOST}.crt
-  key: /${HOST}.key
+  ca: ca.crt
+  cert: ${HOST}.crt
+  key: ${HOST}.key
 
 lighthouse:
   am_lighthouse: ${AM_LIGHTHOUSE:-false}