switch from treehouses sshkey github adduser to addgroup

https://github.com/treehouses/cube/blob/6a6c1ec267d1a39b236721ba845f14383b4bf0e9/src/modules/cube/start_chroot_script#L43-L47

	treehouses sshkey github adduser dogi
	treehouses sshkey github adduser louhdy
	treehouses sshkey github adduser lanxel97
	treehouses sshkey github adduser wesitos
	treehouses sshkey github adduser lmmrssa

Provide feedback