A filed called slave_read_only added in INFO output.

This was an important information missing from the INFO output in the
replication section.

It obviously reflects if the slave is read only or not.

src/redis.c

@@ -2115,7 +2115,10 @@ sds genRedisInfoString(char *section) {
                     (long)server.unixtime-server.repl_down_since);
             }
             info = sdscatprintf(info,
-                "slave_priority:%d\r\n", server.slave_priority);
+                "slave_priority:%d\r\n"
+                "slave_read_only:%d\r\n",
+                server.slave_priority,
+                server.repl_slave_ro);
         }
         info = sdscatprintf(info,
             "connected_slaves:%lu\r\n",