Consolidate jenkins test scripts

There was a lot of duplication between these scripts. Whereas the only
differences were us not doing the following in `jenkins_integration.sh`
which is run against Carrenza:

- Not running unit tests. Which are fast and we wouldn't want to run the
  integration tests if they do fail.
- Publishing the gem. Which I've left in the origin `jenkins.sh`.

We can later change the Carrenza job to run `jenkins_tests.sh` directly and
delete `jenkins_integration_tests.sh`.
Use vcloud-login for integration tests

Writes a temporary FOG_RC containing the API host and username which is used
by both vcloud-login and the integration tests.