UPGRADE

DESCRIPTION
===========
When doing an in-place upgrade using 'mysql_upgrade'
utility (from 5.6/lower to 5.7) followed by export done
through mysqlpump, we get the following error while
importing this dump.

"Invalid default value for {date_field}"

ANALYSIS
========
The default SQL mode in v5.7 includes NO_ZERO_DATE as a
result of which '0000-00-00' (if any) is not permitted in
datetime fields.

One of the ways to allow this is to temporarily suppress
the above mode while importing the data.

FIX
===
Sql_formatter::format_dump_start() has the code which
sets the configuration variables at the top of the dump
file generated through mysqlpump. Added the code to
override the above mode (one of the default sql modes) with
"NO_AUTO_VALUE_ON_ZERO" by setting this value in session
variable 'SQL_MODE'. Resetting to its default value in
Sql_formatter::format_dump_end()