Engine: Dashboard: fix error related to unserialized preferences

With katello running as an engine, we've seen multiple cases
where an error occurs when loading the dashboard.  It appears
that under certain circumstances the preferences are not being
unserialized.  This change will force unserialization, when
necessary.

When it occurs, the stack for the error looks similar to:

no member 'dashboard' in struct

activesupport (3.2.14) lib/active_support/core_ext/object/try.rb:36:in `[]'
activesupport (3.2.14) lib/active_support/core_ext/object/try.rb:36:in `try'
/home/bbucking/github/katello/app/lib/katello/dashboard/layout.rb:41:in `setup_layout'
/home/bbucking/github/katello/app/lib/katello/dashboard/layout.rb:37:in `initialize'
/home/bbucking/github/katello/app/helpers/katello/dashboard_helper.rb:188:in `new'
/home/bbucking/github/katello/app/helpers/katello/dashboard_helper.rb:188:in `dashboard_layout'
/home/bbucking/github/katello/app/helpers/katello/dashboard_helper.rb:193:in `render_dashboard'
/home/bbucking/github/katello/app/views/katello/dashboard/index.html.haml:14:in

A similar issue was reported in:
http://stackoverflow.com/questions/15588643/rails-3-unserialize-returns-only-activerecordattributemethodsserialization
Engine: engine-test-system - system model tests
Engine: org-switcher: updates to support working within engine

This commit contains several changes needed to enable the
org-switcher to work properly within the katello 'as an engine'.
Engine: Fixed changeset_test tests
Merge pull request #3317 from daviddavis/temp/20131105122213

Engine: Fixing changeset tests
Engine: Adding development setup and reset documentation to README.
Engine: Fixed a namespace issue

Made OwnRole extend Katello:Role instead of foreman Role
Merge pull request #3322 from parthaa/own_role

Fixed a namespace issue
Merge pull request #3303 from ehelms/engine-documentation

Engine: Adding development setup and reset documentation to README.
Engine: updating engine install readme
Merge pull request #3327 from komidore64/engine

Engine: updating engine install readme
Engine: Fixing content view tests refs #3585
Merge pull request #3325 from daviddavis/temp/20131106092704

Engine: Fixing content view tests refs #3585
Merge pull request #3310 from bbuckingham/engine-org_switcher

Engine: org-switcher: updates to support working within engine
Merge pull request #3316 from thomasmckay/engine-test-system

Engine: engine-test-system - system model tests
Engine: Fix env model tests, refs #3585
Merge pull request #3329 from daviddavis/temp/20131106133632

Engine: Fix env model tests, refs #3585
Engine: engine-test-org - org model tests

Engine: engine-test-org - partha's fix
Merge pull request #3334 from thomasmckay/engine-test-org

Engine: engine-test-org - org model tests
Engine: fixes #3466 - change Katello logout to Foreman logout path