Use --exclude mongodb-org,mongodb-org-server when installing 2.4.x.

http://docs.mongodb.org/v2.4/tutorial/install-mongodb-on-red-hat-centos-or-fedora-linux/#install-packages
https://jira.mongodb.org/browse/SERVER-13563
Add missing white space before --exclude to fix an installation error.
Merge branch 'feature/mongodb24' into develop to pin mongo version to 2.4.x.