Add correct busybox binary for ppc64le architecture

[svghadi]

This PR is reference to #716. The ppc64le busybox binary currently present in the images is wrong and binary from debian is old hence using ppc64le binary provided by docker-library/busybox.

cc: @dlorenc

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[svghadi]

@googlebot I signed it!

[ghatwala]

LGTM