samples: nvs: Add testing harness

Add console testing harness for expected output.  This allows us
to validate that the test is running properly on hardware.

We expect output of the form (the Reboot_counter will increment
overtime).

Id: 1, Address: 192.168.1.1
Id: 2, Key: ff fe fd fc fb fa f9 f8
Id: 3, Reboot_counter: 5
Id: 4, Data: DATA
Id: 5, Longarray: 0 1 2 3 4 5 6 7 8 9 ... 7f

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>