include run_tests in target name

tools/run_tests/run_tests_matrix.py

@@ -52,14 +52,14 @@ def _safe_report_name(name):
 def _report_filename(name):
     """Generates report file name with directory structure that leads to better presentation by internal CI"""
     # 'sponge_log.xml' suffix must be there for results to get recognized by kokoro.
-    return '%s/%s' % (_safe_report_name(name), 'sponge_log.xml')
+    return 'run_tests_%s/%s' % (_safe_report_name(name), 'sponge_log.xml')
 
 
 def _report_logfilename(name):
     """Generates log file name that corresponds to name generated by _report_filename"""
     # 'sponge_log.log' suffix must be there for log to get recognized as "target log"
     # for the corresponding 'sponge_log.xml' report.
-    return '%s/%s' % (_safe_report_name(name), 'sponge_log.log')
+    return 'run_tests_%s/%s' % (_safe_report_name(name), 'sponge_log.log')
 
 
 def _docker_jobspec(name,