The 'arch' attribute in the conf.yaml is unnecessary, as this can be
readily discovered within the constructor of any given node. Since OS is
determined within user configuration, finding system arch can be done
both reliably and easily within the framework.

For Linux/Posix systems, the 'uname' command is used to determine system
architecture. I believe that this is posix-standard and utilizes a
standardized output.

Bugzilla ID: 1360
Signed-off-by: Nicholas Pratte <npratte@iol.unh.edu>