Quote and qualify parameters explicitly

The gatling test job worked correctly when explicitly built with
parameters via the Jenkins UI, however when triggered by Jenkins itself,
it was failing due to "MissingPropertyException: No such property".

Always quoting and fully qualify parameters explicitly as documented by
the `parameters` documentation[1] resolves the issue and allows the job
to trigger without human intervention.

[1]https://www.jenkins.io/doc/book/pipeline/syntax/#parameters

Bug: Issue 14181
Change-Id: Ifa458f31faecc07c314173bcce941d4a89d55699
diff --git a/jenkins/gatlingTestPipeline.groovy b/jenkins/gatlingTestPipeline.groovy
index ee508bc..24a93d6 100644
--- a/jenkins/gatlingTestPipeline.groovy
+++ b/jenkins/gatlingTestPipeline.groovy
@@ -66,13 +66,13 @@
                         dir ('aws-gerrit/single-master') {
                             script {
                                 def setupData = readFile(file:"setup.env.template")
-                                setupData = resolveParameter(setupData, "HOSTED_ZONE_NAME", HOSTED_ZONE_NAME)
-                                setupData = resolveParameter(setupData, "CLUSTER_INSTANCE_TYPE", CLUSTER_INSTANCE_TYPE)
-                                setupData = resolveParameter(setupData, "DOCKER_REGISTRY_URI", DOCKER_REGISTRY_URI)
-                                setupData = resolveParameter(setupData, "SSL_CERTIFICATE_ARN", SSL_CERTIFICATE_ARN)
+                                setupData = resolveParameter(setupData, "HOSTED_ZONE_NAME", "${params.HOSTED_ZONE_NAME}")
+                                setupData = resolveParameter(setupData, "CLUSTER_INSTANCE_TYPE", "${params.CLUSTER_INSTANCE_TYPE}")
+                                setupData = resolveParameter(setupData, "DOCKER_REGISTRY_URI", "${params.DOCKER_REGISTRY_URI}")
+                                setupData = resolveParameter(setupData, "SSL_CERTIFICATE_ARN", "${params.SSL_CERTIFICATE_ARN}")
 
-                                setupData = resolveParameter(setupData, "METRICS_CLOUDWATCH_NAMESPACE",METRICS_CLOUDWATCH_NAMESPACE)
-                                setupData = resolveParameter(setupData, 'SUBDOMAIN', SUBDOMAIN)
+                                setupData = resolveParameter(setupData, "METRICS_CLOUDWATCH_NAMESPACE", "${params.METRICS_CLOUDWATCH_NAMESPACE}")
+                                setupData = resolveParameter(setupData, 'SUBDOMAIN', "${params.SUBDOMAIN}")
 
                                 setupData = setupData + "\nGERRIT_KEY_PREFIX:= ${GERRIT_KEY_PREFIX}"
                                 setupData = setupData + "\nGERRIT_VOLUME_SNAPSHOT_ID:= ${GERRIT_VOLUME_SNAPSHOT_ID}"