Add missing expirer recon metric to admin_guide
Add missing expirer recon metric to admin_guide

Add expirer/object to recon metrics, which reports such as:

$ curl -s http://localhost:6010/recon/expirer/object
{"object_expiration_pass": 0.19765901565551758, "expired_last_pass": 1}

Change-Id: Ia9a171c09efebe5ad56c9de2952a8f29188c4970

openstack/swift,tipabu/swift,clayg/swift,smerritt/swift,matthewoliver/swift,nadeemsyed/swift,swiftstack/swift,psachin/swift,tipabu/swift,smerritt/swift,hurricanerix/swift,openstack/swift,swiftstack/swift,matthewoliver/swift,psachin/swift,hurricanerix/swift,notmyname/swift,matthewoliver/swift,notmyname/swift,psachin/swift,tipabu/swift,tipabu/swift,hurricanerix/swift,openstack/swift,nadeemsyed/swift,psachin/swift,notmyname/swift,clayg/swift,clayg/swift,smerritt/swift,hurricanerix/swift,swiftstack/swift,nadeemsyed/swift,smerritt/swift,openstack/swift,nadeemsyed/swift,clayg/swift,redbo/swift,notmyname/swift,redbo/swift,matthewoliver/swift