cpu-plug-test: Don't pass integers as strings to device_add

test_plug_with_device_add_x86() plugs Haswell-i386-cpu and
Haswell-x86_64-cpu with device_add.  It passes socket-id, core-id,
thread-id as JSON strings.  The properties are actually integers.

test_plug_with_device_add_coreid() plugs power8_v2.0-spapr-cpu-core
and qemu-s390x-cpu with device_add.  It passes core-id as JSON string.
The properties are actually integers.

Passing JSON string values to integer properties works only due to
device_add implementation accidents.  Fix the test to pass JSON
numbers.  While there, use %u rather than %i with unsigned int.

Cc: Thomas Huth <thuth@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180806065344.7103-14-armbru@redhat.com>

tests/cpu-plug-test.c

@@ -88,8 +88,8 @@ static void test_plug_with_device_add_x86(gconstpointer data)
         for (c = 0; c < td->cores; c++) {
             for (t = 0; t < td->threads; t++) {
                 char *id = g_strdup_printf("id-%i-%i-%i", s, c, t);
-                qtest_qmp_device_add(td->device_model, id, "'socket-id':'%i', "
-                                     "'core-id':'%i', 'thread-id':'%i'",
+                qtest_qmp_device_add(td->device_model, id, "'socket-id':%u, "
+                                     "'core-id':%u, 'thread-id':%u",
                                      s, c, t);
                 g_free(id);
             }
@@ -114,7 +114,7 @@ static void test_plug_with_device_add_coreid(gconstpointer data)
 
     for (c = td->cores; c < td->maxcpus / td->sockets / td->threads; c++) {
         char *id = g_strdup_printf("id-%i", c);
-        qtest_qmp_device_add(td->device_model, id, "'core-id':'%i'", c);
+        qtest_qmp_device_add(td->device_model, id, "'core-id':%u", c);
         g_free(id);
     }