pytest: Use --lazy with umount

Sometimes when doing tests on real hardware we sometimes run in to the
case where some of these mounts haven't been fully flushed.  Using the
--lazy option with umount will allow us to continue while letting the OS
handle flushing the data out still.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/tests/test_ut.py b/test/py/tests/test_ut.py
index e8c8a6d..0b45863 100644
--- a/test/py/tests/test_ut.py
+++ b/test/py/tests/test_ut.py
@@ -213,7 +213,7 @@
               str(exc))
     finally:
         if mounted:
-            u_boot_utils.run_and_log(cons, 'sudo umount %s' % mnt)
+            u_boot_utils.run_and_log(cons, 'sudo umount --lazy %s' % mnt)
         if loop:
             u_boot_utils.run_and_log(cons, 'sudo losetup -d %s' % loop)
 
@@ -274,7 +274,7 @@
               str(exc))
     finally:
         if mounted:
-            u_boot_utils.run_and_log(cons, 'sudo umount %s' % mnt)
+            u_boot_utils.run_and_log(cons, 'sudo umount --lazy %s' % mnt)
         if loop:
             u_boot_utils.run_and_log(cons, 'sudo losetup -d %s' % loop)