Process correctly several test suites in a phpunit test report file

Since SQ 6.0 (see SONAR-7783) SQ fails when saving same metric twice.
Unit test results report file might contain several test suites for the same file (nested). In this case currently we just saving top-most one, other/s are ignored (before SQ 6.0). Since SQ 6.0 analysis will simply fail.

We need to figure out is it legal to nest test suites in PHPUnit format. If it is, we should aggregate data and save it only once.

P.S. In order to avoid analysis failure I've added try/catch which for sure should be removed asap.