rgw-admin: a tool to fix object locator issue

rgw-admin: a tool to fix object locator issue

Objects that start with underscore need to have an object locator,
this is due to an old behavior that we need to retain. Some objects
might have been created without the locator. This tool creates a new
rados object with the appropriate locator.

Syntax:

$ ./radosgw-admin bucket check --check-head-obj-locator \
                               --bucket=<bucket> [--fix]

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
(cherry picked from commit be4355ad8ed622734172fdce77ca71fb2635b36c)