Remove doc/install-guide/section_nova-boot.xml

This should have been removed as part of
https://review.openstack.org/#/c/84638/ - the file is unused now.

Remove it.

Change-Id: Iecfe66394f7899225a67ebcca22680068ff488f2
Fix qemu-nbd disconnect parameter

The parameter is wrong, it should really be /dev/nbd0.

Change-Id: Ifdb858cfa0e4116ca16fbc9c69a9f4f21f872164
Closes-Bug: #1305903
Merge "Remove doc/install-guide/section_nova-boot.xml"
Merge "Fix qemu-nbd disconnect parameter"