bugfix: remove the code that broke XA recovery

sql/log.h

@@ -108,11 +108,7 @@ public:
   int log_and_order(THD *thd, my_xid xid, bool all,
                     bool need_prepare_ordered, bool need_commit_ordered)
   {
-    /*
-      If we are not using WSREP this is an Internal error
-      - TC_LOG_DUMMY::log_and_order() called
-    */
-    DBUG_ASSERT(IF_WSREP(1,0));
+    DBUG_ASSERT(0);
     return 1;
   }
   int unlog(ulong cookie, my_xid xid)  { return 0; }

sql/mysqld.cc

@@ -5101,9 +5101,6 @@ a file name for --log-bin-index option", opt_binlog_index_name);
 
   tc_log= get_tc_log_implementation();
 
-  if (WSREP_ON && tc_log == &tc_log_mmap)
-    tc_log= &tc_log_dummy;
-
   WSREP_DEBUG("Initial TC log open: %s",
               (tc_log == &mysql_bin_log) ? "binlog" :
               (tc_log == &tc_log_mmap) ? "mmap" :