Trying to reconnect to a host after removing a bad key causes the UI to hang

[digimer]

If you try to initialize a host and there's a bad key, you clear the key, and try to connect a second time, the UI hangs.

[digimer]

We need to work together on this. There's an issue where if there's two+ keys with different algos, the user will be prompted to clear bad keys two+ times until the old keys are gone. We need to record that target's IP / hostname in the job, and update the backend to remove all keys for that bad target. For the front end, we need to just change the job data to something like bad_target=192.168.12.1.

[ylei-tsubame]

Related to #706