cmd/snap-seccomp: use upstream seccomp package

cmd/snap-seccomp: use upstream seccomp package

Upstream snapd uses a fork that carries additional compatibility patch
required to build snapd for Ubuntu 14.04. This patch is not required with
the latest snapshot of the upstream seccomp golang bindings but they are
neither released upstream nor backported (in their entirety) to Ubuntu
14.04.

The forked seccomp library is not packaged in Debian. As such, to build
snapd, we need to switch to the regular, non-forked package name.

Signed-off-by: Zygmunt Krynicki <me@zygoon.pl>
Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>
Gbp-Pq: Name 0001-cmd-snap-seccomp-use-upstream-seccomp-package.patch