Correct handling of go test -v output over multiple packages.

Two passing suites in a row resulted in this error:
```
	--- FAIL: Test_parseOutput (0.00 seconds)
		go2xunit_test.go:40: error loading data/gotest.out - orphan output: PASS
```
This commit adds the `PASS` line that `go test -v` emits to the test output and updates the parsing loop to account for it.