Use signals to call Importer and Distributor cancel methods.
Added a few more unit tests for our new signal handlers.
Merge pull request #751 from pulp/mhrivnak-231-release-notes

adding 2.3.1 release notes
Rename graceful_cancel to register_sigterm_handler.
Remove an unused import.
1048297 - pulp-dev.py sets the CA cert and key world readable.

It also makes /etc/pki/pulp/content owned by Apache.
Added Celery and its dependencies to our deps folder.
Pulp depends on python-celery.

Also, don't run Kombu unit tests in Fedora 18.
Fixing a typo in glossary
Merge branch 'pulp-2.3'
Added init scripts and configs for running Celery in Upstart.
Merge branch 'rbarlow-package_distributed_tasks' of github.com:pulp/pulp into rbarlow-package_distributed_tasks
Added the Celery init scripts and environment files to the spec file.
Add our init scripts to pulp-dev.py.
Fixed some line lengths and a spelling error.
Add python-setupttools as a dependency for Celery.
Add support for systemd for starting Celery workers.
Detect the number of processors as the default concurrency on Upstart systems.
Configure pulp_resource_manager to be a symlink in Upstart systems.
Convert pulp_manage_workers into an entry point.