openingd: ensure that initial channel can cover fees and reserve.

This is probably covered by our "channel capacity" heuristic which
requires the channel be significant, but best to be explicit and sure.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/test/run-commit_tx.c

@@ -19,6 +19,13 @@ static bool print_superverbose;
 /* Turn this on to brute-force fee values */
 /*#define DEBUG */
 
+/* AUTOGENERATED MOCKS START */
+/* Generated stub for status_fmt */
+void status_fmt(enum log_level level UNNEEDED, const char *fmt UNNEEDED, ...)
+
+{ fprintf(stderr, "status_fmt called!\n"); abort(); }
+/* AUTOGENERATED MOCKS END */
+
 /* bitcoind loves its backwards txids! */
 static struct bitcoin_txid txid_from_hex(const char *hex)
 {