btrfs: build tag to enable showing version info

be default it is on, with build tags to disable the version info

Signed-off-by: Vincent Batts <vbatts@redhat.com>
Dockerfile: buildtags for old btrfs

Since the build uses ubuntu 14.04, which has an old btrfs, include the
buildtags needed for this old version to not break the build.

Signed-off-by: Vincent Batts <vbatts@redhat.com>