Fixed testing image from being used in non-test artifacts (fixes open-telemetry#170) (open-telemetry#171)

Signed-off-by: Granville Schmidt <1246157+gramidt@users.noreply.github.com>

Resolves Issue: open-telemetry#170

Author: gramidt

Makefile

@@ -102,7 +102,7 @@ prepare-e2e: kuttl set-test-image-vars set-image-controller container
 	$(KUSTOMIZE) build config/crd -o tests/_build/crds/
 
 set-test-image-vars:
-IMG=local/opentelemetry-operator:e2e
+	$(eval IMG=local/opentelemetry-operator:e2e)
 
 # Build the container image, used only for local dev purposes
 container: