Adds existing arch/os information to searches and index operations

This code is a first step in making the current registry aware of
images which are non-Intel architecture.  While os==linux today, if
we are adding architecture we might as well add the pair of arch and
os for future use by Microsoft where os=windows but arch=amd64.

Signed-off-by: Pradipta Kr. Banerjee <bpradip@in.ibm.com>
Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>