azure: tests: reset FAILED status if flaky re-run succeeds

While we already do have logic to re-run flaky tests, the FAILED
variable currently does not get reset to "0". As a result, successful
reruns will still cause the test to be registered as failed.

Fix this by resetting the variable accordingly.

azure-pipelines/test.sh

@@ -54,6 +54,7 @@ run_test() {
 		CLAR_SUMMARY="${BUILD_DIR}/results_${1}.xml" ctest -V -R "^${1}$" || RETURN_CODE=$? && true
 
 		if [ "$RETURN_CODE" -eq 0 ]; then
+			FAILED=0
 			break
 		fi