bmc/general_systemd: Fix cancel

We were using the wrong interface to call the cancel function. It was
supposed to be the Job interface not the Manager interface.

Change-Id: I3bbc622ff51ef7b3a4c2c3ab39a845212707fb77
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/bmc/general_systemd.cpp b/bmc/general_systemd.cpp
index 8d91975..b036bbf 100644
--- a/bmc/general_systemd.cpp
+++ b/bmc/general_systemd.cpp
@@ -30,6 +30,7 @@
 static constexpr auto systemdService = "org.freedesktop.systemd1";
 static constexpr auto systemdRoot = "/org/freedesktop/systemd1";
 static constexpr auto systemdInterface = "org.freedesktop.systemd1.Manager";
+static constexpr auto jobInterface = "org.freedesktop.systemd1.Job";
 
 bool SystemdNoFile::trigger()
 {
@@ -85,7 +86,7 @@
 
     // Cancel the job
     auto cancel_req = bus.new_method_call(systemdService, job->c_str(),
-                                          systemdInterface, "Cancel");
+                                          jobInterface, "Cancel");
     try
     {
         bus.call_noreply(cancel_req);