The following are included in the switch to strict confinement:
* Set snapcraft.yaml confinement to strict and restore/update plugs
* Drop building of python as it's not required for strict snaps
* Switch back to running apps under root
* Patch setgroups from ngnix since it's not covered by a plug
* Build libxml into snap
Change-Id: Ibd2e3c625ceb92cb4b6dd9f0c9a9012baf7c53a5
da4138e3f5