I discussed with Shilpa and got to know that zone rename command information had to be added in 'radosgw-admin --help' command output, not in man page.
As required information on 'zone rename' has been added in 'radosgw-admin --help', moving bug to VERIFIED state.
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$ sudo radosgw-admin --help |grep zone
zone create create a new zone
zone delete delete a zone
zone get show zone cluster params
zone modify modify an existing zone
zone set set zone cluster params (requires infile)
zone list list all zones set on this cluster
zone rename rename a zone
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Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHSA-2016-2815.html