When a check constraint expression contains a column using function
defaults (Like CURTIME(), CURRENT_TIMESTAMP, CURDATE()), for a
operation if default value is used for such column then constraint
was evaluated incorrectly.

Currently default value for columns using function defaults or
default expression is set very late, after CHECK OPTION and
check constraints evaluation. For a DML operation if value for a
column is supposed to come from the function defaults then check
constraint expression uses NULL as a value for column instead
of correct default value. As result check constraint is evaluated
incorrectly.

The sequence of execution should be 1) set function defaults
2) invoke before triggers 3) CHECK OPTION 4) CHECK CONSTRAINTS.
In the current code, this sequence is followed only when BEFORE
triggers are defined on the table. Otherwise 1 is executed
after 4. To fix this issue, corrected the execution sequence.

Correcting sequence of execution fixes even Bug29834066 "DEFAULT
EXPRESSION CAN BREAK VIEW CHECK OPTION". Issue here is, INSERT
into views evaluate default expression / function after CHECK OPTION
is performed. As result it is possible to insert rows into view
with CHECK OPTION which won't be visible in the view, which
CHECK OPTION is supposed to prevent.

Reviewed by : Dmitry Lenev <dmitry.lenev@oracle.com>

Change-Id: Ib16f7c32d597b80cc78506a7ace53dea6dcb0088