Add some missing include files which break build in certain platforms

Two files were using functions from <sys/stat.h> but not including
in. Most of the time they got this automatically via another header,
but certain build flag combinations can reveal the problem

* src/lxc/lxc_container.c, src/node_device/node_device_linux_sysfs.c:
  Add <sys/stat.h>

src/lxc/lxc_container.c

@@ -32,6 +32,7 @@
 #include <sys/ioctl.h>
 #include <sys/mount.h>
 #include <sys/wait.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #include <mntent.h>
 

src/node_device/node_device_linux_sysfs.c

@@ -23,6 +23,7 @@
 #include <config.h>
 
 #include <fcntl.h>
+#include <sys/stat.h>
 
 #include "node_device_driver.h"
 #include "node_device_hal.h"