As discussed in https://issues.jenkins-ci.org/browse/JENKINS-33557?focusedCommentId=251657&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-251657 and confirmed in the next comment, there's indeed a bug with 2.x :

Welcome to Jenkins v2! Click here to install the rest of v2 functionalities and finish the upgrade process

is displayed even for totally fresh instance.

To reproduce easily with a locally built/downloaded jenkins.war:

docker run -v $PWD/jenkins.war:/jenkins.war:ro -p 10000:8080 -it java:7 java -jar /jenkins.war