{import,export}_raw_vdi use vhd-tool via vhd_tool_wrapper

This allows both functions to use O_DIRECT.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 7de0edee16116204619d6634fc22bd4d8af5b745)

Conflicts:
	ocaml/xapi/OMakefile
	ocaml/xapi/import_raw_vdi.ml
{import,export}_raw_vdi: update Task.progress

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit b89c237fb27c29b369ea37559f7a91133eef80f3)
VDI.export: allow the user to specify a format; currently either 'raw' or 'vhd'

The HTTP handler accepts an additional argument:

  GET /export_raw_vdi?vdi=<vdi>&format=<raw|vhd>...

The content-disposition HTTP header is used to suggest a useful filename, and
the content-type HTTP header is set to either application/octet-stream or
application/vhd.

The CLI accepts an optional argument:

  xe vdi-export uuid=<uuid> filename=<filename> [format=(raw|vhd)]

.vhd format export will require a newer vhd-tool (>= 0.6.5)

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 59fa5ee62bbc6e05939b2b0538ff15aae4ea6d6b)
import_raw_vdi: normalise whitespace

$ camlp4o -printer o -no_comments ocaml/xapi/import_raw_vdi.ml | md5sum
e74faa7367f4c06d818a04fd87dfeeb5
$ git checkout HEAD^
$ camlp4o -printer o -no_comments ocaml/xapi/import_raw_vdi.ml | md5sum
e74faa7367f4c06d818a04fd87dfeeb5

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 6c16a13da45adae59e557a4f9e9543911b530804)

Conflicts:
	ocaml/xapi/import_raw_vdi.ml
import_raw_vdi: support importing vhd-format data

This requires vhd-tool >= 0.6.6

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 99abc50518d5bb76f6b9f93927865f7273d1acb4)

Conflicts:
	ocaml/xapi/import_raw_vdi.ml
xe vdi-import: add support for [type=(raw|vhd)]

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit be7acec752d6439acfbb8ba5ab4951a677fc7e1b)
VDI.export: add /dev/mapper to the vhd parent search path

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 7f60bff7f25325d97d23ff14b82ce8ea0e6b386b)
VDI.export: add a 'base' argument to export only VDI differences

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
(cherry picked from commit 62590b892b74ae0facb67123fc9e7cb8f3ca78d2)