buffet: Fix CallMethodAndBlock callsites in command.cc

We built up a lot of CLs while the CQ stalled, and not all of them were
compatible with each other.

BUG=None
TEST=unittests

Change-Id: I547fddf7d06290cb521b5213e1640040a320d2a4
Reviewed-on: https://chromium-review.googlesource.com/218892
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>

buffet/libbuffet/command.cc

diff --git a/buffet/libbuffet/command.cc b/buffet/libbuffet/command.cc
index e9f9e6c..67db6a5 100644
--- a/buffet/libbuffet/command.cc
+++ b/buffet/libbuffet/command.cc
@@ -36,25 +36,29 @@
   chromeos::dbus_utils::CallMethodAndBlock(GetObjectProxy(),
                                            dbus_constants::kCommandInterface,
                                            dbus_constants::kCommandSetProgress,
+                                           nullptr,
                                            progress);
 }
 
 void Command::Abort() {
   chromeos::dbus_utils::CallMethodAndBlock(GetObjectProxy(),
                                            dbus_constants::kCommandInterface,
-                                           dbus_constants::kCommandAbort);
+                                           dbus_constants::kCommandAbort,
+                                           nullptr);
 }
 
 void Command::Cancel() {
   chromeos::dbus_utils::CallMethodAndBlock(GetObjectProxy(),
                                            dbus_constants::kCommandInterface,
-                                           dbus_constants::kCommandCancel);
+                                           dbus_constants::kCommandCancel,
+                                           nullptr);
 }
 
 void Command::Done() {
   chromeos::dbus_utils::CallMethodAndBlock(GetObjectProxy(),
                                            dbus_constants::kCommandInterface,
-                                           dbus_constants::kCommandDone);
+                                           dbus_constants::kCommandDone,
+                                           nullptr);
 }
 
 int Command::GetProgress() const {