reenroll errored loop

[groob]

it's possible for the launcher to fail to re-enroll and never get back into a good state due to user error. Repro:

1. start with a good enroll secret at /etc/launcher/secret
2. while the launcher is in a good state, edit the enroll secret to break it.
3. return node_invalid = true from the server some time after a successful enrollment. Launcher will attempt one of the "doXWithReenroll" method, ex

{"caller":"extension.go:323","component":"launcher","err":"enrollment invalid, reenrollment errored: enrollment invalid","level":"debug","msg":"generating configs with reenroll failed","ts":"2018-11-01T03:13:21.628981Z"}

There's no exit out of this currently.