[#301] rpc: Make client stream initialization get cancelled by dial timeout

* `c.conn` may be already invalidated but the rpc client can't detect this.
  `NewStream` may hang trying to open a stream with invalidated connection.
  Using timer with `dialTimeout` for `NewStream` fixes this problem.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

api/rpc/client/init.go

@@ -52,6 +52,7 @@ func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageRe
 	}
 
 	ctx, cancel := context.WithCancel(prm.ctx)
+	defer cancel()
 
 	// `conn.NewStream` doesn't check if `conn` may turn up invalidated right before this invocation.
 	// In such cases, the operation can hang indefinitely, with the context timeout being the only
@@ -79,14 +80,12 @@ func (c *Client) Init(info common.CallMethodInfo, opts ...CallOption) (MessageRe
 		select {
 		case <-newStreamCh:
 		default:
-			cancel()
 			return nil, context.Canceled
 		}
 	case <-newStreamCh:
 	}
 
 	if err != nil {
-		cancel()
 		return nil, err
 	}