Change search success criterium

Change search success criterium

When running a step in the binary search, we can now change the
behaviour by adding a new parameter in the [test] section of the
test file: generator_threshold. The default value for this parameter
is set to inf, which results in the same behaviour as before this
change was implemented. The relative difference between what the
cores can generate and what is actually sent into the generator's
interface must be lower than the generator_threshold, for the test
to be successful.

Signed-off-by: Luc Provoost <luc.provoost@gmail.com>
Change-Id: Id3e787b3571bdb9f241763fceaffccb9ea81a264