test_xml_output: add tests for valid duration for tests
test_xml_output: add tests for valid duration for tests

This is to check for the case where the duration is not -1
or in [0, CK_DEFAULT_TIMEOUT]. There was an issue with NO_FORK
mode where the duration was not valid.

tarruda/check,tarruda/check,tarruda/check,tarruda/check,tarruda/check