This WL moves the actions executed by the MySQL upgrade client to the mysqld
proper.The MySQL server will then have control of when these actions are
executed, and is not dependent on user to run the mysql_upgrade client.

The mysql_upgrade client still exists, but will return EXIT_ALREADY_UPGRADED
on normal usage and SUCCESS when used with --force option.

MySQL upgrade client steps in the past
======================================

Step 1. Fix mysql schema - the system tables. (Executing
mysql_system_tables.sql + mysql_system_tables_fix.sql +
mysql_system_tables_data_fix.sql)
Step 2. Fix sys schema tables. (Executing mysql_sys_schema.sql)
Step 3. Running CHECK TABLE on all tables. If the status of any of the tables
is not "OK", we either REPAIR the tables or ALTER the tables based on the
response from CHECK TABLE.

New server options
==================

--no-upgrade - to abort if upgrade is needed, to avoid accidental upgrades.
--minimal-upgrade - start a new server on the old data directory, upgrading DD
but skipping the upgrade of the server.This option will simulate the older
behaviour of in-place upgrade.
--force-upgrade - To force run server upgrade sequence.

The new upgrade steps
=====================

1. If DD version in dd_properties is not the latest, upgrade DD tables.
2. Set new DD version and server version in dd_properties table and commit.
3. If server version in dd_properties is not the latest OR server version in
dd_properties does not match the latest upgraded server version, upgrade system
tables.
4. Make a note of the latest upgraded server version in dd_properties table and
commit.

During in-place upgrade, if DD upgrade goes well, but Server upgrade happens to
fail, the server exits. Subsequent server starts would attempt an upgrade and
fail again (provided the server upgrade failure is repeatable) to start since
the new server version isn't set yet. Now the user is stuck with a data
directory with newer DD tables but older system tables. And the server would
not be operational with this data directory.

To help fix this situation, we introduce a new server option to skip server
upgrade - minimal-upgrade. With this, we will skip the steps 3 and 4 of the new
upgrade sequence mentioned above. This is the same as the current behaviour of
in-place upgrade.

We do not want to allow upgrading a server which has been started with
--minimal-upgrade. This is to make sure that an upgrade is completed
successfully before moving to a newer version.

Change-Id: Ifce818e7acb5eb0704ba1ebda36e48f83a58b92a