Disable warnings for 'drop if exists' and 'create if not exist' commands

mysql-test/columnstore/devregression/t/mcs7124_regression_bug3798.test

@@ -9,11 +9,16 @@
 USE tpch1;
 #
 select cidx, CDOUBLE, CAST(CDOUBLE AS DECIMAL(9)) from datatypetestm order by cidx;
+--disable_warnings
 drop table if exists bug3798;
+--enable_warnings
+
 create table bug3798 (c1 float) engine=columnstore;
 insert into bug3798 values (1234567), (1.2345678);
 select c1, cast(c1 as decimal(9,2)), cast(c1 as decimal(14,12)) from bug3798;
-drop table bug3798;
 
+--disable_warnings
+drop table bug3798;
+--enable_warnings
 #