cmd/coordinator: fix another UI issue with trybots against old Go releases

Updates golang/go#28580
Updates golang/go#17626

Change-Id: Ifa88e4ad23e823e5d1a25c46b76afb11b4e7907b
Reviewed-on: https://go-review.googlesource.com/c/147497
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: bradfitz

cmd/coordinator/coordinator.go

@@ -664,7 +664,7 @@ func serveTryStatusHTML(w http.ResponseWriter, ts *trySet, tss trySetState) {
 		}
 		bs.mu.Unlock()
 		fmt.Fprintf(buf, "<tr valign=top><td align=left>%s</td><td align=center>%s</td><td><pre>%s</pre></td></tr>\n",
-			bs.Name,
+			html.EscapeString(bs.NameAndBranch()),
 			status,
 			bs.HTMLStatusLine())
 	}