a bootstatus field to the nodes table. os_setup sets this to one of
okay, failed, unknown. This is to be used with the still to be defined
method of specifying certain nodes that can fail reboot on experiment
creation. Right now sharks are wired to this, and this information is
presented in the web page. Its also essential for the batch system,
which needs to consider nodes that failed to reboot, or else batch
experiments would never end. Might still need a way for an experiment
to tell the batch system its done though.