Some REST API calls cause the JIRA instance to respond with a 404:

<status>
 <status-code>404</status-code>
 <message>null for uri: ...</message>
</status>

The problem shows up when JIRA site URL is set to something like: http://example.com/jira/.

For example, when the REST client requests available project versions, no versions are displayed in Jenkins and the log reports:

Sep 11, 2015 1:23:22 PM hudson.plugins.jira.JiraRestService getVersions
WARNING: jira rest client get versions error. cause: Not Found