Make UTF-8 characters display correctly in the web ui

Some valid UTF-8 characters don't display correctly on the web ui,
like F09F8CAE (taco emoji). This adds the proper meta element to
the <head> so they display correctly.

Change-Id: I872c84a93d22f1cabce4534eccc917df99079414
Reviewed-on: http://gerrit.cloudera.org:8080/3830
Tested-by: Kudu Jenkins
Reviewed-by: Todd Lipcon <todd@apache.org>
diff --git a/src/kudu/server/webserver.cc b/src/kudu/server/webserver.cc
index 858e485..1121ccb 100644
--- a/src/kudu/server/webserver.cc
+++ b/src/kudu/server/webserver.cc
@@ -378,6 +378,7 @@
 const char* const PAGE_HEADER = "<!DOCTYPE html>"
 " <html>"
 "   <head><title>Kudu</title>"
+" <meta charset='utf-8'/>"
 " <link href='/bootstrap/css/bootstrap.min.css' rel='stylesheet' media='screen' />"
 " <link href='/kudu.css' rel='stylesheet' />"
 " </head>"