sanitycheck: Making child thread exits when main thread dies

Set threads spawned by BinaryHandler dameon, so when the main thread
exits for some unusual reason (e.g SIGINT) the child threads are
automatically killed.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
diff --git a/scripts/sanitycheck b/scripts/sanitycheck
index e774f0a..e83c346 100755
--- a/scripts/sanitycheck
+++ b/scripts/sanitycheck
@@ -581,7 +581,7 @@
 
         with subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=self.build_dir) as proc:
             verbose("Spawning BinaryHandler Thread for %s" % self.name)
-            t = threading.Thread(target=self._output_reader, args=(proc, harness, ))
+            t = threading.Thread(target=self._output_reader, args=(proc, harness, ), daemon=True)
             t.start()
             t.join(self.timeout)
             if t.is_alive():