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_tests.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 original `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.
Prevent token from being logged by Jenkins

Disable `set -x` in all Jenkins scripts so that the FOG_VCLOUD_TOKEN
environment variable is never logged by Jenkins. These scripts are fairly
simple so we shouldn't lose much by disabling bash debugging.

And explicitly disable debugging with `set +x` just before we set the token,
to guard against the possibility of someone unwittingly re-enabling this in
the future.
Merge pull request #45 from gds-operations/vcloud_login_tests

[#68989754 #72170126] Use vcloud-login for tests