stable futures fixes (#1124)

* Fix eth1 update functions

* Fix genesis and client

* Fix beacon node lib

* Return appropriate runtimes from environment

* Fix test rig

* Refactor eth1 service update

beacon_node/beacon_chain/src/eth1_chain.rs

@@ -285,8 +285,10 @@ impl<T: EthSpec, S: Store<T>> CachingEth1Backend<T, S> {
     }
 
     /// Starts the routine which connects to the external eth1 node and updates the caches.
-    fn start(&self, exit: tokio::sync::oneshot::Receiver<()>) {
-        tokio::spawn(HttpService::auto_update(self.core.clone(), exit));
+    pub fn start(&self, exit: tokio::sync::oneshot::Receiver<()>) {
+        // don't need to spawn as a task is being spawned in auto_update
+        // TODO: check if this is correct
+        HttpService::auto_update(self.core.clone(), exit);
     }
 
     /// Instantiates `self` from an existing service.