Update mysql recipe to not use mysql::default

This recipe is no longer in newer versions of the mysql cookbook and so
gerrit::mysql will fail in wrapper cookbooks using newer versions.

Replacing it with client has the same effect as 3.0.4 of the mysql
cookbook which this cookbook is currently pinned to.
Merge pull request #12 from QuickbridgeLtd/remove-mysql-default

Update mysql recipe to not use mysql::default