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/script/tf-coverity/common-def.sh b/script/tf-coverity/common-def.sh
index fc88ba0..bec96fc 100644
--- a/script/tf-coverity/common-def.sh
+++ b/script/tf-coverity/common-def.sh
@@ -38,7 +38,7 @@
 # infrastructure)
 is_arm_jenkins_env() {
     if [ "$JENKINS_HOME" ]; then
-	if echo "$JENKINS_URL" | grep -q "oss.arm.com"; then
+	if echo "$JENKINS_PUBLIC_URL" | grep -q "oss.arm.com"; then
 	    return 0;
 	fi
     fi