cmd/coordinator: test sharding, better status, logs

Also gomote updates which came about during the process of developing
and debugging this.

Change-Id: Ia53d674118a6b99bcdda7062d3b7161279b6ad52
Reviewed-on: https://go-review.googlesource.com/10463
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/buildlet/buildletclient.go b/buildlet/buildletclient.go
index f555045..a840744 100644
--- a/buildlet/buildletclient.go
+++ b/buildlet/buildletclient.go
@@ -105,6 +105,8 @@
 	return "http://" + strings.TrimSuffix(c.ipPort, ":80")
 }
 
+func (c *Client) IPPort() string { return c.ipPort }
+
 func (c *Client) do(req *http.Request) (*http.Response, error) {
 	if c.password != "" {
 		req.SetBasicAuth("gomote", c.password)