According to Zimbra support, this is a known issue:
Bug 24884 - zmtlsctl doesn't update zimbra.web.xml.in or zimbraAdmin.web.xml.in
and they offer the following workaround:
su - zimbra
cp /opt/zimbra/jetty/etc/zimbra.web.xml.in /tmp/zimbra.web.xml.in
edit /opt/zimbra/jetty/etc/zimbra.web.xml.in, and remove the "REDIRECT" section, it's close to the bottom of the file.
zmtlsctl http
zmcontrol stop
zmcontrol start
At this point, http mode should be working. If you wish to use the "both" mode, you can run:
zmtlsctl both
zmcontrol stop
zmcontrol start
Hope this helps!