More work on procstats: save/restore state, fixes.

We now persistent the current procstats to storage
to keep them across boots.  Still need to do division
and pruning across days; right now they will just keep
collecting forever.

Also fix some bugs in the checkin output.

Change-Id: I4dd9317dbe2ee0642af8f2f0be1f2bd9c4055e80