--plain should not return an error if there are no matching issues

[febs]

using jira issue list to search for issues returns error code 1 no matter if the command fails for any technical issues (DNS error, host unreachable etc) or if the command runs successfully but there are no queries matching the search string.

To be able to properly use the command in a wrapper script, jira-cli should return no error if there is no issues matching the query, it's just that there are issue... not an error. Or at least, distinguish a failure in connecting and getting the issues from a legitimate, but empty, answer, by using a different return code.

Thanks,