tools: Plumb in capture control

Add control of capturing output into u_boot_pylib and the tools which
use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/__main__.py b/tools/patman/__main__.py
index 0d08a53..db78ea6 100755
--- a/tools/patman/__main__.py
+++ b/tools/patman/__main__.py
@@ -38,7 +38,7 @@
         from patman import test_checkpatch
 
         result = test_util.run_test_suites(
-            'patman', False, False, False, None, None, None,
+            'patman', False, False, False, False, None, None, None,
             [test_checkpatch.TestPatch, func_test.TestFunctional,
              'settings'])