rgw: fix obj copied from remote gateway acl full_control issue

rgw: fix obj copied from remote gateway acl full_control issue

This part of the code is commit in
ea3efca

When copy a object to a remote gateway, the check processing which is
done by
"Bitwise And" between source object's acl elements and
grants_headers_def array elements
will be done to produce the target object's acl elements.

So when the full_control is the first element of grants_headers_def, no
matter the
source object's acl element permission field is write or read, the
result of
bitwise and will always be true, then call grants_by_type_add_one_grant
with
check_perm which is full_control, all of the permission field of the
target object's
acl elements will be full_control.

Fixes: http://tracker.ceph.com/issues/20658
Signed-off-by: Enming Zhang <enming.zhang@umcloud.com>