router: log vshard version during configuration

Users usually come to developers with logs, this logs has Tarantool's
version in it, but vshard version is missing there. Let's log version,
so that developers don't have to always ask users, which vshard version
is used there.

Part of #612

NO_DOC=internal
NO_TEST=minor

Author: Serpentian

vshard/router/init.lua

@@ -1231,11 +1231,8 @@ end
 local function router_cfg(router, cfg, is_reload)
     cfg = lcfg.check(cfg, router.current_cfg)
     local vshard_cfg = lcfg.extract_vshard(cfg)
-    if not M.replicasets then
-        log.info('Starting router configuration')
-    else
-        log.info('Starting router reconfiguration')
-    end
+    log.info('Starting router %sconfiguration at VShard %s',
+             M.replicasets and 're' or '', consts.VERSION)
     if vshard_cfg.box_cfg_mode ~= 'manual' then
         local box_cfg = lcfg.extract_box(cfg, {})
         log.info("Calling box.cfg()...")