Configure limit of opened files for the test runner process

For some reason, when Tobiko retries many times ssh connection
and logs a lot of data in the log file, pytest may fail with
"Too many open files" exception raised.
To avoid that lets try to configure soft ulimit for opened files
to be as high as possible (same as hard limit).

Change-Id: I6fb8977d7909798a5ab6be499044cc74ac34dfa2

tools/run_tests.py

@@ -16,6 +16,7 @@ from __future__ import absolute_import
 
 import os
 import psutil
+import resource
 import signal
 import sys
 import subprocess
@@ -106,6 +107,7 @@ def main():
 
 
 def run_tests():
+    setup_ulimits()
     setup_timeout()
     cleanup_report_dir()
     log_environ()
@@ -122,6 +124,16 @@ def run_tests():
     return succeeded
 
 
+def setup_ulimits():
+    try:
+        hard_nofile_limit = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
+        resource.setrlimit(
+            resource.RLIMIT_NOFILE,
+            (hard_nofile_limit, hard_nofile_limit))
+    except ValueError:
+        pass
+
+
 def setup_timeout():
 
     if RUN_TESTS_TIMEOUT > 0.: