Set password for mysql root user on undercloud

The port is firewalled off by default so mysql is not reachable except
to localhost users. In any case it is good to set a password for the
mysql root user.

We are 'reusing' the user_db_password parameter, because it is actually
unused, instead of adding yet another parameter.

Tested this change against an existing undercloud and observed that
the mysql root user got a correct password and that the /root/.my.cnf
file got generated.

Closes-Bug: #1742191

Change-Id: I408ce3a0fe2ab8e86bcc280256cdb51688efde75

elements/puppet-stack-config/puppet-stack-config.yaml.template

@@ -234,6 +234,7 @@ tripleo::profile::base::database::mysql::mysql_server_options:
     bind-address: "%{hiera('controller_host')}"
     innodb_file_per_table: 'ON'
 mysql::server::restart: true
+mysql::server::root_password: {{UNDERCLOUD_DB_PASSWORD}}
 
 # Neutron
 neutron::debug: "%{hiera('debug')}"

instack_undercloud/undercloud.py

@@ -380,7 +380,7 @@ _opts = [
 # Passwords, tokens, hashes
 _auth_opts = [
     cfg.StrOpt('undercloud_db_password',
-               help=('Password used for MySQL databases. '
+               help=('Password used for MySQL root user. '
                      'If left unset, one will be automatically generated.')
                ),
     cfg.StrOpt('undercloud_admin_token',

undercloud.conf.sample

@@ -222,7 +222,7 @@
 # From instack-undercloud
 #
 
-# Password used for MySQL databases. If left unset, one will be
+# Password used for MySQL root user. If left unset, one will be
 # automatically generated. (string value)
 #undercloud_db_password = <None>