libxl: Increase device model startup timeout to 1min.

On a busy host, QEMU may take more than 10s to load and start.

This is likely due to a bug in Linux where the I/O subsystem sometime
produce high latency under load and result in QEMU taking a long time to
load every single dynamic libraries.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
(cherry picked from commit 9acfbe14d7)

Conflicts:
	tools/libxl/libxl_internal.h
(cherry picked from commit bbbd29a25d)

tools/libxl/libxl_internal.h

@@ -83,7 +83,9 @@
 #define LIBXL_INIT_TIMEOUT 10
 #define LIBXL_DESTROY_TIMEOUT 10
 #define LIBXL_HOTPLUG_TIMEOUT 10
-#define LIBXL_DEVICE_MODEL_START_TIMEOUT 10
+/* QEMU may be slow to load and start due to a bug in Linux where the I/O
+ * subsystem sometime produce high latency under load. */
+#define LIBXL_DEVICE_MODEL_START_TIMEOUT 60
 #define LIBXL_QEMU_BODGE_TIMEOUT 2
 #define LIBXL_XENCONSOLE_LIMIT 1048576
 #define LIBXL_XENCONSOLE_PROTOCOL "vt100"