enable vnfsdk to support multi-arch

    enable 2 functions:
    1, build images for amd64/arm64
    2, push image with multi-arch support

Change-Id: I50702c7797de674c67475c4c0dab6d55830a0d60
Signed-off-by: Bin Lu <bin.lu@arm.com>
Issue-ID: VNFSDK-319
2 files changed