Don't infinitely append configuration to files

[maxolasersquad]

If options are chosen foor Google's AIY then the script will inifinitely append configuration changes to file each time the setup is run.

This commit will overwrite the google repository apt file and only append to the boot configuration if the configuration doesn't already exist.

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[maxolasersquad]

Any chance of getting some love on this PR?

[LearnedVector]

@maxolasersquad this works for me. Sorry for the delay.