Bump appc/docker2aci library version to 0.15.0

[ybubnov]

This patch bumps the version of the appc/docker2aci library to 0.15.0
in order to support the conversion of the images with various os/arch.

fixes #3526

[ghost]

Can one of the admins verify this patch?

[ybubnov]

The output of the command, used to download the ubuntu image for aarch64:

$ sudo ./build-rkt-1.22.0+git/target/bin/rkt --debug --insecure-options=image fetch docker://aarch64/ubuntu:latest
image: remote fetching from URL "docker://aarch64/ubuntu:latest"
image: fetching image from docker://aarch64/ubuntu:latest
Downloading sha256:1f8c28d8b7a [=============================]     859 B / 859 B
Downloading sha256:7e21759f0cb [=============================]     169 B / 169 B
Downloading sha256:9dbf9f34817 [=============================]     467 B / 467 B
Downloading sha256:8944e166ce9 [=============================] 46.4 MB / 46.4 MB
Downloading sha256:5cb9db57901 [=============================]     684 B / 684 B
sha512-8fcbbea543851539105f05f7c73a4adf

[lucab]

ok to test

[glevand]

I tested this and it seems to fix #3526 (fetch: arch messed up).

$ sudo ./rkt --debug --insecure-options=image fetch docker://aarch64/busybox:latest
image: remote fetching from URL "docker://aarch64/busybox:latest"
image: fetching image from docker://aarch64/busybox:latest
Downloading sha256:8df7d836248 [=============================] 1.77 MB / 1.77 MB
sha512-5489fe0c84402cd7d843c35197066adb
$ sudo ./rkt image list 
ID                      NAME                                            SIZE    IMPORT TIME     LAST USED
sha512-5489fe0c8440     registry-1.docker.io/aarch64/busybox:latest     6.6MiB  4 seconds ago   3 seconds ago

[s-urbaniak]

LGTM, the fedora 24 failure is a known flake

[lucab]

Great, right in time for 1.23.0! Merging.