qom: Refine container_get() to allow using a custom root

Specify the root to search from as argument. This avoids hardcoding
"/machine" in some places and makes it more flexible.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
index 81d6548..dc4e4e1 100644
--- a/hw/qdev-monitor.c
+++ b/hw/qdev-monitor.c
@@ -181,7 +181,7 @@
     static Object *dev;
 
     if (dev == NULL) {
-        dev = container_get("/machine/peripheral");
+        dev = container_get(qdev_get_machine(), "/peripheral");
     }
 
     return dev;
@@ -192,7 +192,7 @@
     static Object *dev;
 
     if (dev == NULL) {
-        dev = container_get("/machine/peripheral-anon");
+        dev = container_get(qdev_get_machine(), "/peripheral-anon");
     }
 
     return dev;