Added check for active pair in onopen

Because the timeout makes the pair inactive, we should check for this
state in onopen before connecting to the client. Updated tests to set
the proxy pair to active before testing onopen. Also removed a
redundant statement.

proxy/snowflake.js

@@ -86,8 +86,6 @@ class Snowflake {
             return pair.active = false;
           }
         }), 20000); // 20 second timeout
-      } else {
-        return pair.active = false;
       }
     }, function() {
       return pair.active = false;