Install default users directly

Install default users directly

Install /home/ast and /home/bin as part of the system build procedure,
as the setup script is not ran on the arm image.

/home/bin is needed for successful completion of our test suite.

This patch does not change the setup script, as it is not bothered by
those files/directiories being already there, and may be useful during
reinstallation on intel systems.

Change-Id: I358c881df09223c343442673aa0822937f9ea33c