change persistent flag to be an enum off/on/auto
Change-Id: I3b1685ea76afb3b7f8c2e6ca63fbf81fa987750e
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27100
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>