fix: ``wait_for_tcp_port`` would not work as expected and always succeed.

``$DEFAULT_BASH_IMAGE`` would not be set (because not exported) and as consequence
the ``docker run`` would fail with an errorlevel different from 1. The failure
condition was bogus here, and we should not rely on ``$DEFAULT_BASH_IMAGE`` to be
exported. Both have been corrected.

bin/compose-core

@@ -695,11 +695,12 @@ wait_docker_ip() {
 }
 export -f wait_docker_ip
 
-DEFAULT_BASH_IMAGE=${DEFAULT_BASH_IMAGE:-docker.0k.io/bash}
 wait_for_tcp_port() {
     local network=$1 host_port=$2 timeout=20
     verb "Trying to connect to $host_port"
-    docker run --rm -i --network "$network" "$DEFAULT_BASH_IMAGE" <<EOF
+    bash_image=${DEFAULT_BASH_IMAGE:-docker.0k.io/bash}
+    echo docker run --rm -i --network "$network" "$bash_image" >&2
+    docker run --rm -i --network "$network" "$bash_image" <<EOF
     start=\$SECONDS
     while true; do
         timeout 1 bash -c "</dev/tcp/${host_port/://}" >/dev/null 2>&1 && break