checkcommits: Fix tests running in a CI environment.
checkcommits: Fix tests running in a CI environment.

TestGetCommitAndBranch() was failing in a CI environment as it was
triggering the CI-detection code.  Unset all CI variables after saving
them for sane test behaviour.

Signed-off-by: James O. D. Hunt <348fbaadfbada55ea105602bf5609e23ac1c4898@intel.com>

clearcontainers/tests,GabyCT/tests,bwarden/tests,devimc/tests,clearcontainers/tests,devimc/tests,MarioCarrilloA/tests,chavafg/tests,GabyCT/tests,sboeuf/tests,sboeuf/tests,bwarden/tests,MarioCarrilloA/tests,chavafg/tests