fixtures: Unpin puppetlabs-mysql module
fixtures: Unpin puppetlabs-mysql module

Since commit dd25406 of puppet-openstacklib we don't need to pin a
specific release of puppetlabs-mysql.

Change-Id: Ia8cc39d89a5005badede03aee8bc0818a1dfc4a1

rdo-puppet-modules/puppet-tuskar