Fix usage of wrong env variable in default-user.groovy

Author: foxylion

docker-images/master/default-user.groovy

@@ -7,7 +7,7 @@ def jenkins = Jenkins.getInstance()
 jenkins.setSecurityRealm(new HudsonPrivateSecurityRealm(false))
 jenkins.setAuthorizationStrategy(new GlobalMatrixAuthorizationStrategy())
 
-def user = jenkins.getSecurityRealm().createAccount(env.JENKINS_USER, env.JENKINS_PASSWORD)
+def user = jenkins.getSecurityRealm().createAccount(env.JENKINS_USER, env.JENKINS_PASS)
 user.save()
 
 jenkins.getAuthorizationStrategy().add(Jenkins.ADMINISTER, 'admin')