CI: Manually fix CI build
CI: Manually fix CI build

The CIRCLE_PULL_REQUEST variable has some problems with not being set,
so comparing head to master seems to be the better idea in ensuring that
the current build does not skip in a merge.
https://discuss.circleci.com/t/circle-pull-request-not-being-set/14409/21

Signed-off-by: Kosy Anyanwu <519f5f08e431fb38e06b0e978780a5dcb63e1f73@kinvolk.io>

kinvolk/habitat-operator,kinvolk/habitat-operator