Packagesets are only editable by ubuntu techboard

[Julian Edwards]

As per the code in the security adapter below. This is bad because we want derived distros to add their own packagesets.

class EditPackagesetSet(AuthorizationBase):
    permission = 'launchpad.Edit'
    usedfor = IPackagesetSet

    def checkAuthenticated(self, user):
        """Users must be an admin or a member of the tech board."""
        return user.in_admin or user.in_ubuntu_techboard