Specify "pygrub" by default for libxl backend guests.

Using an absolute path prevents libxl from providing the correct
default.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Closes: #770485

debian/patches/debian/Pygrub-path.patch

+From: Ian Campbell <ijc@debian.org>
+Date: Fri, 21 Nov 2014 13:45:51 +0000
+Subject: allow libxl to find default path to pygrub.
+
+The Xen debian packages relocate pygrub into
+/usr/lib/xen-X.Y/bin/pygrub, not /usr/bin/pygrub. Since libxl knows to
+DTRT with a bare "pygrub" just use that by default.
+
+--- a/src/libxl/libxl_conf.h
++++ b/src/libxl/libxl_conf.h
+@@ -53,7 +53,7 @@
+ # define LIBXL_LIB_DIR LOCALSTATEDIR "/lib/libvirt/libxl"
+ # define LIBXL_SAVE_DIR LIBXL_LIB_DIR "/save"
+ # define LIBXL_DUMP_DIR LIBXL_LIB_DIR "/dump"
+-# define LIBXL_BOOTLOADER_PATH BINDIR "/pygrub"
++# define LIBXL_BOOTLOADER_PATH "pygrub"
+ 
+ /* libxl interface for setting VCPU affinity changed in 4.5. In fact, a new
+  * parameter has been added, representative of 'VCPU soft affinity'. If one

debian/patches/series

+debian/Pygrub-path.patch
 debian/remove-RHism.diff.patch
 debian/Don-t-enable-default-network-on-boot.patch
 debian/fix-Debian-specific-path-to-hvm-loader.patch