Replace JENKINS_URL with JENKINS_PUBLIC_URL

To ensure tf-a-ci-scripts can run on both OpenCI
and Arm Test CI, JENKINS_URL has been replaced with
JENKINS_PUBLIC_URL, as JENKINS_URL is a reserved
private URL in Arm infrastructure.

JENKINS_PUBLIC_URL is a system-wide environment
variable and was configured in:
Manage Jenkins > System > Global Properties

Default values:
OpenCI Production Jenkins: https://ci.trustedfirmware.org/
OpenCI Staging Jenkins: https://ci.staging.trustedfirmware.org/
arm test CI: https://jenkins.openci-test.arm.com/

Change-Id: I3ddf9ebc12f2c9bf045366ee548f23df12656f8f
Signed-off-by: Arthur She <arthur.she@linaro.org>
diff --git a/job/tf-ci-gateway/generate_report.sh b/job/tf-ci-gateway/generate_report.sh
index 89d4468..32e99f4 100755
--- a/job/tf-ci-gateway/generate_report.sh
+++ b/job/tf-ci-gateway/generate_report.sh
@@ -30,7 +30,7 @@
 	fi
 
 	# set proper jobs names for test generation report script
-	if echo "$JENKINS_URL" | grep -q "oss.arm.com"; then
+	if echo "$JENKINS_PUBLIC_URL" | grep -q "oss.arm.com"; then
 		worker_job="${worker_job:-tf-worker}"
 		lava_job="${lava_job:-tf-build-for-lava}"
 	else