tests: cleanup test directory

- add a `pkg` directory for packages
- add a `cases` directory for yml files

Signed-off-by: Dave Tucker <dt@docker.com>

test/cases/test-kernel-config.yml

@@ -0,0 +1,31 @@
+kernel:
+  image: "linuxkit/kernel:4.9.x"
+  cmdline: "console=ttyS0"
+init:
+  - linuxkit/init:63eed9ca7a09d2ce4c0c5e7238ac005fa44f564b
+  - linuxkit/runc:b0fb122e10dbb7e4e45115177a61a3f8d68c19a9
+  - linuxkit/containerd:18eaf72f3f4f9a9f29ca1951f66df701f873060b
+  - linuxkit/ca-certificates:5fc6ba7f91534ddbfef975404c33e44581e6ed7a
+onboot:
+  - name: dhcpcd
+    image: "linuxkit/dhcpcd:8837289b78ecd80f59524883085424e115dd0b3a"
+    binds:
+     - /var:/var
+     - /tmp:/etc
+    capabilities:
+     - CAP_NET_ADMIN
+     - CAP_NET_BIND_SERVICE
+     - CAP_NET_RAW
+    net: host
+    command: ["/sbin/dhcpcd", "--nobackground", "-f", "/dhcpcd.conf", "-1"]
+  - name: check-kernel-config
+    image: "mobylinux/kernel-config:c9e41ab96b3ea6a3ced97634751e20d12a5bf52f"
+    pid: host
+    capabilities:
+     - CAP_SYS_BOOT
+    readonly: true
+outputs:
+  - format: kernel+initrd
+  - format: iso-bios
+  - format: iso-efi
+  - format: gcp-img