Fixed failures for privilege_table_io and wsrep_cluster_address_basic

- Sometimes privilege_table_io printed double rows of roles_mapping
  - Fixed by forcing restart of server when running test
- Wsrep_cluster_address_basic failed in some combinations because
  wsrep_cluster_address was set to NULL
  - Fixed by ensuring it's never set to NULL, only empty string

mysql-test/suite/perfschema/t/privilege_table_io.test

 # Tests for PERFORMANCE_SCHEMA table io
+# This test makes a restart because without it, events_waits_history_long
+# sometimes contains duplicated entries of roles_mapping.
 
 --source include/not_embedded.inc
 --source include/have_perfschema.inc
+--source include/restart_mysqld.inc
 --source ../include/table_io_setup_helper.inc
 
 # Remove "deleted" records from mysql.db that may come from previous tests,

sql/wsrep_mysqld.cc

@@ -805,7 +805,7 @@ void wsrep_init_startup (bool first)
      (wsrep_on_fun)wsrep_on);
 
   /* Skip replication start if no cluster address */
-  if (!wsrep_cluster_address || strlen(wsrep_cluster_address) == 0) return;
+  if (!wsrep_cluster_address || wsrep_cluster_address[0] == 0) return;
 
   if (first) wsrep_sst_grab(); // do it so we can wait for SST below
 
@@ -918,7 +918,7 @@ bool wsrep_start_replication()
     return true;
   }
 
-  if (!wsrep_cluster_address || strlen(wsrep_cluster_address)== 0)
+  if (!wsrep_cluster_address || wsrep_cluster_address[0]== 0)
   {
     // if provider is non-trivial, but no address is specified, wait for address
     wsrep_ready_set(FALSE);

sql/wsrep_var.cc

@@ -359,11 +359,11 @@ bool wsrep_cluster_address_check (sys_var *self, THD* thd, set_var* var)
       (var->save_result.string_value.length > (FN_REFLEN - 1))) // safety
     goto err;
 
-  memcpy(addr_buf, var->save_result.string_value.str,
-         var->save_result.string_value.length);
-  addr_buf[var->save_result.string_value.length]= 0;
+  strmake(addr_buf, var->save_result.string_value.str,
+          sizeof(addr_buf)-1);
 
-  if (!wsrep_cluster_address_verify(addr_buf)) return 0;
+  if (!wsrep_cluster_address_verify(addr_buf))
+    return 0;
 
  err:
   my_error(ER_WRONG_VALUE_FOR_VAR, MYF(0), var->var->name.str,
@@ -421,8 +421,8 @@ void wsrep_cluster_address_init (const char* value)
               (wsrep_cluster_address) ? wsrep_cluster_address : "null", 
               (value) ? value : "null");
 
-  if (wsrep_cluster_address) my_free ((void*)wsrep_cluster_address);
-  wsrep_cluster_address = (value) ? my_strdup(value, MYF(0)) : NULL;
+  my_free((void*) wsrep_cluster_address);
+  wsrep_cluster_address= my_strdup(value ? value : "", MYF(0));
 }
 
 /* wsrep_cluster_name cannot be NULL or an empty string. */