fix: overbilling for failed patches

[eseidel]

If you install patch 1. Patch 2 then fails to boot (install) and rolls back to patch 1 we will bill you for patch 1 twice (since we report successful install of patch 1 again).

[eseidel]

Clarified with Bryan, this shouldn't happen for automatic rollbacks (which don't download anything new, only revert to a previously booting patch or the unaltered release), only explicit rollbacks (where explicit downloads do happen).

So I may have been mistaken in filing this.

[bryanoltman]

As written, this is not correct. Patch 2 would need to successfully install before failing in order to trigger 1) a patch install success event to be sent and 2) patch 1 to be uninstalled.

[bryanoltman]

Currently the only time where this happens (patch N+1 successfully installs and we later revert back to patch N) is in the case of a rollback of patch N+1, where billing for more than one install of patch N is correct.