Force conformance tests to fail properly (nginxinc#1786)

Problem: If the conformance test Pod runner failed, the `make` process would still pass. This is because the failure code would not propagate to outside of the Pod.

Solution: After the Pod runs, check the exit code and fail it it's non-zero. Used a bash script for this because running the `kubectl get pod` command in the Makefile would not return an Errored Pod for some reason. Only worked in bash.

conformance/Makefile

@@ -103,6 +103,7 @@ run-conformance-tests: ## Run conformance tests
 		--restart=Never -- sh -c "go test -v . -tags conformance,experimental -args --gateway-class=$(GATEWAY_CLASS) \
 						        --supported-features=$(SUPPORTED_FEATURES) --version=$(VERSION) \
 								--report-output=output.txt; cat output.txt" | tee output.txt
+	bash scripts/check-pod-exit-code.sh
 	sed -e '1,/CONFORMANCE PROFILE/d' output.txt > conformance-profile.yaml
 	rm output.txt
 	[ $(shell cat conformance-profile.yaml | yq '.profiles[0].core.result') != "failure" ] \

conformance/scripts/check-pod-exit-code.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+CODE=$(kubectl get pod conformance -o jsonpath='{.status.containerStatuses[].state.terminated.exitCode}')
+if [ $CODE -ne 0 ]; then
+    exit 2
+fi