Allow stale master status to be assigned via maxadmin

If a master once had slaves and is in the stale status, it will not retain
this status after a restart. Without storing on-disk information, the
stale master status cannot be deduced by looking at the master
alone. Because of this, the user should be able to manually enable the
stale master status.

Documentation/Reference/MaxAdmin.md

@@ -520,6 +520,10 @@ The status bit that can be controlled are
     <td>maintenance</td>
     <td>The server is in maintenance mode. In this mode no new connections will be established to the server. The monitors will also not monitor servers that are in maintenance mode.</td>
   </tr>
+  <tr>
+    <td>stale</td>
+    <td>The server is a stale master server. Read [MySQL Monitor](../Monitors/MySQL-Monitor.md) documentation for more details.</td>
+  </tr>
 </table>
 
 

server/core/server.c

@@ -990,6 +990,7 @@ static struct
     { "ndb",         SERVER_NDB },
     { "maintenance", SERVER_MAINT },
     { "maint",       SERVER_MAINT },
+    { "stale",       SERVER_STALE_STATUS },
     { NULL,          0 }
 };