Run delete/abort fails when Polygraph is in some broken states

[LionsPhil]

Plumage does not recover well from some inconsistent states where runs have failed, because attempts to clean up across all the machines involved become fatal. For example, if there's a problem with the connectivity between the client and server, e.g. the proxy under test is misconfigured or misbehaving, the polygraph server side can time out and shut down.

Delete actions on the master should tolerate the client or server reporting that they are unable to delete the run in question and still continue trying to clean up the run locally.

In the meantime, the workaround is to (in order, since some steps may unblock later steps):

1. SSH onto the server, check for and kill any running polygraph processes, and clean out /run/plumage/server/.
2. Repeat for the client and /run/plumage/client/. If there were polygraph processes to kill, be patient; this may unjam the process and start reporting results back to the master.
3. SSH onto the master, look under /var/lib/plumage/configurations/N/runs/ (where N is in the URL of the configuration), and delete the directory matching the broken run number.