Added fetch & reset to refresh existing repo.

When bootstrap is run more than once on a machine, the existing git
checkout is now refreshed instead of just used as is.
Merge branch 'refresh_existing_git_clone' of git://github.com/rca/salt-bootstrap into develop
Support Fedora in `tests/install-testsuite-deps.py`.
Fedora does not need to enable `epel-testing` repo.
Remove extra `salt`.
Remove git from cleanup.
Disable the salt git develop install test because salt's develop branch is not always installable and the test cannot fail because of that.
Include Debian based distributions support into `tests/install-testsuite-deps.py`.
No user input.
Also uninstall the dependencies between Debian based test runs.
Merge branch 'develop' of github.com:saltstack/salt-bootstrap into issues/57