Removed lock wait timeout warning when using CREATE TABLE IF EXISTS

mysql-test/r/create.result:
  Added test case to show that CREATE TABLE also is not waiting if table exists.
mysql-test/t/create.test:
  Added test case to show that CREATE TABLE also is not waiting if table exists.
sql/sql_base.cc:
  Clear also warnings from acquire_locks if we retry.

mysql-test/r/create.result

@@ -2416,6 +2416,12 @@ create table if not exists t1 (a int, b int) select 2,2;
 ERROR 42S01: Table 't1' already exists
 create table if not exists t1 like t2;
 ERROR 42S01: Table 't1' already exists
+create table t1 (a int, b int);
+ERROR 42S01: Table 't1' already exists
+create table t1 (a int, b int) select 2,2;
+ERROR 42S01: Table 't1' already exists
+create table t1 like t2;
+ERROR 42S01: Table 't1' already exists
 select * from t1;
 a	b
 1	1

mysql-test/t/create.test

@@ -2013,6 +2013,12 @@ create table if not exists t1 (a int, b int);
 create table if not exists t1 (a int, b int) select 2,2;
 --error ER_TABLE_EXISTS_ERROR
 create table if not exists t1 like t2;
+--error ER_TABLE_EXISTS_ERROR
+create table t1 (a int, b int);
+--error ER_TABLE_EXISTS_ERROR
+create table t1 (a int, b int) select 2,2;
+--error ER_TABLE_EXISTS_ERROR
+create table t1 like t2;
 disconnect user1;
 connection default;
 select * from t1;

sql/sql_base.cc

@@ -4779,6 +4779,7 @@ lock_table_names(THD *thd,
     */
     if (check_if_table_exists(thd, tables_start, 1, &exists))
       DBUG_RETURN(TRUE);                       // Should never happen
+    thd->warning_info->clear_warning_info(thd->query_id);
     thd->clear_error();                        // Forget timeout error
     if (exists)
     {