Conform ODL with last framework updates

Conform ODL with last framework updates

Now ODL TestCase calculates the ratio between critical tests passed
and failed and saves it in result. Non-critical test cases can fail as
result doesn't take them into account [1].

It also updates default attribute values in TestCase and allows result
to be float.

[1] http://robotframework.org/robotframework/latest/RobotFrameworkUserGuide.html#setting-criticality

Change-Id: Id4a89271b5b1a90cd3c1e2b08591ff26ffaffee0
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>