dom0/spec: mark qrexec policy as config files
dom0/spec: mark qrexec policy as config files

Prevent override on upgrade, when user makes some own changes (especially
"always allow" feature).

marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin