Fix recursive call in delete alternate server (#1250)

I tested the code part by using manual and automated tools for more than
2 years.

Fixes #823 

When you try to delete an alternate server in the list by using "das :" command on the CLI, the session gets stuck and can't response although alternate server is removed.

The problem appears to be related to calling del_alt_server function in the same function recursively.

Co-authored-by: CUMHUR KARAHAN <[email protected]>

src/apps/relay/netengine.c

@@ -265,7 +265,6 @@ static void del_alt_server(const char *saddr, int default_port, turn_server_addr
           TURN_LOG_FUNC(TURN_LOG_LEVEL_INFO, "Alternate server removed: %s\n", s);
         }
 
-        del_alt_server(saddr, default_port, list);
       }
     }