peer_control: don't complete fundchannel command until broadcast.

Under stress, the tests can mine blocks too soon, and the funding never
locks.  This gives more of a chance, at least.

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

tests/test_lightningd.py

@@ -148,6 +148,8 @@ class LightningDTests(BaseLightningDTests):
 
         l1.rpc.addfunds(tx)
         l1.rpc.fundchannel(l2.info['id'], amount)
+        # Technically, this is async to fundchannel.
+        l1.daemon.wait_for_log('sendrawtx exit 0')
 
         l1.bitcoin.rpc.generate(6)