Fix issue in sentinel logic for gathering healthy slaves

Author: ryaneorth

lib/resty/redis/sentinel.lua

@@ -39,7 +39,11 @@ function _M.get_slaves(sentinel, master_name)
                 host[slave[i]] = slave[i + 1]
             end
 
-            if host["master-link-status"] == "ok" then
+            local master_link_status_ok = host["master-link-status"] == "ok"
+            local is_down = host["flags"] and (string.find(host["flags"],"s_down")
+                or string.find(host["flags"],"o_down")
+                or string.find(host["flags"],"disconnected"))
+            if master_link_status_ok and not is_down then
                 host.host = host.ip -- for parity with other functions
                 tbl_insert(hosts, host)
             end