Add monitored plugin restart delay
Add monitored plugin restart delay

Implements a simple backoff mechanism to introduce increasing delays
in plugin restart to avoid chewing up CPU while trying to restart
a badly-configured plugin as fast as possible. Needs a test.

intel-hpdd/lemur,intel-hpdd/lemur,intel-hpdd/lemur,intel-hpdd/lemur,intel-hpdd/lemur,intel-hpdd/lemur