Docker: run directory for post-start if present.

Also, fix the case where we didn't use --network with EXPOSE_TCP,
as reported by @theborakompanioni:

```
I get Wrong network! Our Bitcoin backend is running on 'regtest', but we expect 'main'. with LIGHTNINGD_NETWORK := regtest when param --network is not provided.
```

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

tools/docker-entrypoint.sh

@@ -4,18 +4,24 @@
 
 networkdatadir="${LIGHTNINGD_DATA}/${LIGHTNINGD_NETWORK}"
 
-if [ "$EXPOSE_TCP" == "true" ]; then
-    set -m
-    lightningd "$@" &
+set -m
+lightningd --network="${LIGHTNINGD_NETWORK}" "$@" &
 
-    echo "Core-Lightning starting"
-    while read -r i; do if [ "$i" = "lightning-rpc" ]; then break; fi; done \
+echo "Core-Lightning starting"
+while read -r i; do if [ "$i" = "lightning-rpc" ]; then break; fi; done \
     < <(inotifywait -e create,open --format '%f' --quiet "${networkdatadir}" --monitor)
-    echo "Core-Lightning started"
+
+if [ "$EXPOSE_TCP" == "true" ]; then
     echo "Core-Lightning started, RPC available on port $LIGHTNINGD_RPC_PORT"
 
     socat "TCP4-listen:$LIGHTNINGD_RPC_PORT,fork,reuseaddr" "UNIX-CONNECT:${networkdatadir}/lightning-rpc" &
-    fg %-
-else
-    exec lightningd --network="${LIGHTNINGD_NETWORK}" "$@"
 fi
+
+# Now run any scripts which exist in the lightning-poststart.d directory
+if [ -d "$LIGHTNINGD_DATA"/lightning-poststart.d ]; then
+    for f in "$LIGHTNINGD_DATA"/lightning-poststart.d/*; do
+	"$f"
+    done
+fi
+
+fg %-