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>
(cherry picked from commit a813bdf49920a1295f56caa9f79f33334150c911)
diff --git a/script/gen_merge_report.sh b/script/gen_merge_report.sh
index e40263e..1d60875 100644
--- a/script/gen_merge_report.sh
+++ b/script/gen_merge_report.sh
@@ -9,7 +9,7 @@
 REPORT_JSON=$1
 REPORT_HTML=$2
 
-if echo "$JENKINS_URL" | grep -q "oss.arm.com"; then
+if echo "$JENKINS_PUBLIC_URL" | grep -q "oss.arm.com"; then
   ARTIFACT_PATH='artifact/html/qa-code-coverage'
   INFO_PATH='coverage.info'
   JSON_PATH='intermediate_layer.json'
@@ -35,7 +35,7 @@
 import os
 import re
 
-server = os.getenv("JENKINS_URL", "https://jenkins.oss.arm.com/")
+server = os.getenv("JENKINS_PUBLIC_URL", "https://jenkins.oss.arm.com/")
 merge_json = {} # json object
 _files = []
 with open("$REPORT_JSON") as json_file: