Run the History persister only on the leading server.

(02:59:39 PM) wsorenson_hs_: i think some of the managed stuff needs to only run on the master
(02:59:54 PM) wsorenson_hs_: for instance the history persister

this changes the persister to only run on the leading master.
Remove @Nonnull from primitive fields
Merge pull request #365 from hgschmie/run-persister-only-on-master

Run the History persister only on the leading server.
Merge pull request #366 from hgschmie/primitives-can-not-be-null

Remove @Nonnull from primitive fields
use proper delete  function
Merge branch 'master' of github.com:HubSpot/Singularity