Support new deployments on mysql 8.0

[rg2011]

Trying to deploy a new keystone server with a mysql database in version 8.0 yields the following error:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL
server version for the right syntax to use near 'IDENTIFIED BY 'keystone' at line 1.

It is because of these commands in the launch script:

fiware-keystone-spassword/docker/postlaunchconfig.sh

Lines 54 to 58 in 71f6ecc

	CREATE DATABASE keystone;
	GRANT ALL PRIVILEGES ON keystone.* TO 'keystone'@'localhost' \
	IDENTIFIED BY 'keystone';
	GRANT ALL PRIVILEGES ON keystone.* TO 'keystone'@'%' \
	IDENTIFIED BY 'keystone';

Mysql 8 deprecates the syntax GRANT ... IDENTIFIED BY, requiring two separate statements (CREATE USER and GRANT PRIVILEGES). See https://stackoverflow.com/questions/13357760/mysql-create-user-if-not-exists

Mysql 5.7, on the other hand, might not support CREATE USER ...IF NOT EXISTS. So a full solution to this problem should try both syntaxes to support both versions.

[fgalan]

PR #233