Use canonical MySQL root pwd reset procedure

[Petr Malik]

Use canonical MySQL root pwd reset procedure

Current Implementation:
Trove restores InnoDB backups by operating directly on the file system.
This means that the restored database would still use
the old (and potentially no longer available) root password.
Trove therefore needs to reset the password on the restored databases.
This was originally done by starting the service in the
safe mode (which allows root login without password) and
executing 'SET PASSWORD FOR ...' statement to reset the password.

Proposed Improved Solution:
The recommended generic procedure for resetting a 'forgotten' root
password is documented in the official MySQL doc:
http://dev.mysql.com/doc/refman/5.6/en/resetting-permissions.html

This recommended procedure, as opposed to the original one,
is also compatible with other MySQL-derived datastores.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/152262
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=1017d6824e79ba811d9b4e4361c881ac5654bf06
Submitter: Jenkins
Branch: master

commit 1017d6824e79ba811d9b4e4361c881ac5654bf06
Author: Petr Malik <email address hidden>
Date: Fri Jan 30 13:27:42 2015 -0500

    Use canonical MySQL root pwd reset procedure

    Current Implementation:
    Trove restores InnoDB backups by operating directly on the file system.
    This means that the restored database would still use
    the old (and potentially no longer available) root password.
    Trove therefore needs to reset the password on the restored databases.
    This was originally done by starting the service in the
    safe mode (which allows root login without password) and
    executing 'SET PASSWORD FOR ...' statement to reset the password.

    Proposed Improved Solution:
    The recommended generic procedure for resetting a 'forgotten' root
    password is documented in the official MySQL doc:
    http://dev.mysql.com/doc/refman/5.6/en/resetting-permissions.html

    Added '--skip-grant-tables' to 'mysqld_safe' startup parameters.
    That is required for unrestricted access to the user table.
    The server can be instructed to start using grant tables at any
    time by executing 'FLUSH PRIVILEGES' statement.
    Added '--skip-networking' to prevent anybody from sneaking in
    across the network while resetting the root password.
    Replaced the password-reset statement with a direct user table update
    followed by 'FLUSH PRIVILEGES'.
    Removed '--protocol' parameter from the mysqladmin shutdown call,
    as we started the database with '--skip-networking' and the guestagent
    is running locally anyways.
    We also check for errors in the password-reset stage,
    so that a proper error message (including cause) can be logged.

    Tested with MySQL 5.5/5.6 and Percona

    Closes-Bug: 1419995
    Change-Id: I86777c4177cb46d61573c564335b529d7a1da52a