debug output of main script

ext/central-controller-docker/main-new.sh

@@ -165,3 +165,8 @@ export GLIBCXX_FORCE_NEW=1
 export GLIBCPP_FORCE_NEW=1
 export LD_PRELOAD="/opt/conda/envs/central_controller/lib/libjemalloc.so.2"
 exec /usr/local/bin/zerotier-one -p${ZT_CONTROLLER_PORT:-$DEFAULT_PORT} /var/lib/zerotier-one
+if [ $? -ne 0 ]; then
+    echo '*** FAILED: zerotier-one exited unexpectedly'
+    cat /var/lib/zerotier-one/local.conf
+    exit 1
+fi