Inconsistent behavior detecting whether MySQL needs to be installed

[robamaton]

Ubuntu 12.04 LTS
Chef 11.10

https://github.com/aws/opsworks-cookbooks/blob/release-chef-11.10/mysql/recipes/client.rb

I have two layers, a Rails App layer and a Delayed Job layer for background workers. I'm using RDS with the MySQL engine, but not actually attaching it to the OpsWorks stack, since I want to attach multiple stacks to a single RDS instance.

In the Rails App layer, the first line of mysql::client:
if node[:opsworks][:layers].has_key?('db-master') || (node[:opsworks][:stack][:rds_instances].any?{|rds_instance| rds_instance[:engine] == 'mysql'}) is returning true, even though there is no 'db-master' layer, and no RDS instances associated with the stack. However, instances in the Delayed Job layer (which also has the mysql::client recipe on setup) has that line return false, so I have to specify "libmysqlclient-dev" under OS Packages.

This only started recently, and before I never had to specify the OS Package separately.