DurationAssertion does not seem to make difference between Main sample only and Main sample and sub-samples for time

@pmouawad ([Bug 54156](https://bz.apache.org/bugzilla//show_bug.cgi?id=54156&redirect=false)):
I may be wrong but I don't see in JMeterThread#checkAssertions code:
if (scopedAssertion.isScopeParent(scope) || scopedAssertion.isScopeAll(scope) || scopedAssertion.isScopeVariable(scope)){
processAssertion(parent, assertion);
}

Code passes parent whether parent or Parent+Subsamples are selected and DurationAssertion uses response.getTime() which does not make the difference between parent and parent+sub samples.

Related to 51939

See:
http://mail-archives.apache.org/mod_mbox/jmeter-user/201211.mbox/%3CDF8EC4058D0FD04583D2DFDBD3934C210FD75512%40SIXPRD0410MB395.apcprd04.prod.outlook.com%3E

Severity: normal
OS: All

Depends on:
* https://github.com/apache/jmeter/issues/2576