Add unsupported_hardware option to the cmdline

This option disables the warning that blocks
installation on the hardware that is not
supported by this CentOS release.

Change-Id: Iac13fd39a154f6b524c2c9ccfa10351a150999a4
Closes-Bug: 1322502
Merge "Add unsupported_hardware option to the cmdline" into stable/5.0