[server] --rpc_default_keepalive_time_ms is not runtime

The --rpc_default_keepalive_time_ms flag is not runtime: the messenger
for a Kudu server created in ServerBase::Init() using current value of
the flag and the parameter cannot be changed later on.

Change-Id: Id79bb22d7ce424a37b0a61b75c054906e7de0d1c
Reviewed-on: http://gerrit.cloudera.org:8080/16476
Tested-by: Kudu Jenkins
Reviewed-by: Grant Henke <granthenke@apache.org>
diff --git a/src/kudu/server/server_base.cc b/src/kudu/server/server_base.cc
index dcc8afd..3ccede8 100644
--- a/src/kudu/server/server_base.cc
+++ b/src/kudu/server/server_base.cc
@@ -103,7 +103,6 @@
 DEFINE_int64(rpc_negotiation_timeout_ms, 3000,
              "Timeout for negotiating an RPC connection.");
 TAG_FLAG(rpc_negotiation_timeout_ms, advanced);
-TAG_FLAG(rpc_negotiation_timeout_ms, runtime);
 
 DEFINE_bool(webserver_enabled, true, "Whether to enable the web server on this daemon. "
             "NOTE: disabling the web server is also likely to prevent monitoring systems "