failed add-machine ssh: leaves behind garbage in state

debugging some other issues with manual provider and ssh (lack of use of ssh-agent on add-machine even though its used in bootstrap).. i came across a bunch of garbage being left behind in state even though the command failed. any reason juju can't clean up after itself when it knows the add-machine failed?

$ juju status
environment: ocean
machines:
  "0":
    agent-state: started
    agent-version: 1.21-alpha1.1
    dns-name: 192.241.202.97
    instance-id: 'manual:'
    series: trusty
    hardware: arch=amd64 cpu-cores=2 mem=3953M
    state-server-member-status: has-vote
  "1":
    agent-state: pending
    dns-name: 192.241.217.243
    instance-id: manual:192.241.217.243
    series: trusty
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "2":
    agent-state: pending
    dns-name: 162.243.153.228
    instance-id: manual:162.243.153.228
    series: trusty
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "3":
    agent-state: pending
    dns-name: 107.170.196.104
    instance-id: manual:107.170.196.104
    series: trusty
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "4":
    agent-state: pending
    dns-name: 192.241.201.218
    instance-id: manual:192.241.201.218
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "5":
    agent-state: pending
    dns-name: 192.241.236.187
    instance-id: manual:192.241.236.187
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "6":
    agent-state: pending
    dns-name: 192.241.213.226
    instance-id: manual:192.241.213.226
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "7":
    agent-state: pending
    dns-name: 192.241.201.218
    instance-id: manual:192.241.201.218
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "8":
    agent-state: pending
    dns-name: 192.241.217.243
    instance-id: manual:192.241.217.243
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "9":
    agent-state: pending
    dns-name: 192.241.236.187
    instance-id: manual:192.241.236.187
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "10":
    agent-state: pending
    dns-name: 192.241.217.243
    instance-id: manual:192.241.217.243
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
  "11":
    agent-state: pending
    dns-name: 192.241.236.187
    instance-id: manual:192.241.236.187
    series: precise
    hardware: arch=amd64 cpu-cores=2 mem=2001M
services: {}