Looking at bug 10410 and the screenshot attached, you can see the icon the button. The code still exists in the bootstrap theme, but does not use the bootstrap icon. http://bugs.koha-community.org/bugzilla3/attachment.cgi?id=18651
Still valid, also for the Finish button: <button type="submit" class="btn"><i class="icon finish"></i> Finish</button> No icon displays.
*** This bug has been marked as a duplicate of bug 22274 ***