Use time in suite if provided

I have a junit xml like this:

```xml

```

(this is from the output of https://www.npmjs.com/package/jest-junit)

### Expected

I expect the suites' totals.duration to match the time mentioned in the `testsuite` itself rather than be the sum of times in testcases.

### Actual

The totals.duration is the sum of the testcases. This leaves out the time spent by the testsuite in setup and teardown which is not part of any 1 individual test case.