Add network block device package to support LXC rootfs mount on it.

This fix the bug 970645.

Change-Id: If9fde90ac71cdaaff0d006a4df1a325f6f656744
xenapi: /boot/guest should point to local SR

Fixes bug 1037516

This patch creates a directory os-guest-kernels inside the local SR, and
sets up /boot/guest to be a symlink to that directory. This way
OpenStack won't pollute Dom0's filesystem.

Change-Id: If8dfe24355bd782a401fed0f2c4b423efd9c11ba
Merge "xenapi: /boot/guest should point to local SR"
Merge "Add network block device package to support LXC rootfs mount on it."