[Linaro:ARM_CI] Stop using ambe config as not needed
Please cherry pick this into the r2.12 branch to keep it able to build aarch64 with the CI scripts. The ambe config was removed from the docker container used to build this branch and so this cherry pick is needed to keep the branch able to build for aarch64. Without this cherry pick, the scripts will abort and no wheels will be produced for aarch64. For reference, the r2.12 commit that broke aarch64 build: https://github.com/tensorflow/tensorflow/commit/6fa05df43b00038b048f4f0e51ef522da6532fec

The use of the ambe config to build and test aarch64 is not needed and so stop using it. The ambe config will be removed in the future so this must be done in preparation. Also make cpu_arm64_pip.sh and cpu_arm64_nonpip.sh more similar for easier future maintenance.