CI: Jenkins: Drop CI env var - we don't use it
CI: Jenkins: Drop CI env var - we don't use it

afaict the CI env var is only used by the fetchbranches tool, and we
do not call the fetchbranches tool under Jenkins, as we have already
done the pull/merge work in this script (and do not set the
PULL_REQUEST_NUMBER or LOCALCI_PR_NUMBER as required in .ci/setup.sh
before invoking fetchbranches.

Unset the CI env var, as un-used

Signed-off-by: Graham Whaley <95f36e5ac6982f4574a5c449c37cf652e934d2b9@intel.com>

MarioCarrilloA/tests,devimc/tests,devimc/tests,MarioCarrilloA/tests,clearcontainers/tests,chavafg/tests,clearcontainers/tests,chavafg/tests