oeqa/selftest/sstatetests: prettier output for allarch test
Instead of creating two lists of full paths and comparing them which in failure
produces a list of every stamp file (so all tasks, twice), reduce the filename
down to a recipe/task->hash dictionary and compare those, meaning unittest
shows the differences in the dictionaries.
In the future get_files() should be generalised so all tests in this class can
use it, and find a pair of hashes that don't match and run diffsigs on them.
Signed-off-by: Ross Burton <ross.burton@intel.com>
