v2v: Add some assertions to check the source was created correctly.

(cherry picked from commit dbe35729a3fbb7150275584dd0c5aa7d86c8e03e)
v2v: -i libvirtxml: Fix handling of nbd sources (RHBZ#1153589).

Previously I modified the parse_libvirt_xml function to get rid of the
awkward 'map_source*' functions, and have the callers map over and
modify the source disks afterwards.  However this broke the case where
an "nbd:..." URL was returned by parse_libvirt_xml, since the callers
might try to map this URL (eg. turning it into an absolute path).
This broke virt-p2v specifically.

This commit changes parse_libvirt_xml to return a list of tuples
containing disk information, giving the callers more information with
which to do the mapping.

This fixes commit 3596165282ccf2c5896894ec4e9a71c6da788463.

(cherry picked from commit ad78d1492b02eaf5d810e2f9d012a5fed4f4124b)
RHEL 7: Emphasize libguestfs-winsupport package (RHBZ#627468).

This RHEL-only patch changes the error messages when the
inspection code cannot find an operating system inside the guest
image.  For a Windows guest this may happen because the user has not
installed the separate 'libguestfs-winsupport' package.  Therefore we
emphasize that the user may need to install this package.

Notes:

(1) In RHEL there are two pieces of inspection code, the old Perl code
(deprecated upstream) and the new C core inspection API.  Therefore
this patch has to touch two places with essentially the same change.

(2) This patch doesn't try to be clever and detect if it was a Windows
guest.  This should reduce the chance of failure.

Output from (Perl) virt-inspector now looks like this:

 $ virt-inspector disk.img
 No operating system could be detected inside this disk image.

 This may be because the file is not a disk image, or is not a virtual machine
 image, or because the OS type is not understood by virt-inspector.

 If you feel this is an error, please file a bug report including as much
 information about the disk image as possible.

 RHEL notice
 -------------
 libguestfs will return this error for Microsoft Windows guests if the
 separate 'libguestfs-winsupport' package is not installed. If the
 guest is running Microsoft Windows, please try again after installing
 'libguestfs-winsupport'.

Output from guestfish (ie. C core inspection API) now looks like this:

 $ guestfish -i disk.img
 guestfish: no operating system was found on this disk

 RHEL notice
 -------------
 libguestfs will return this error for Microsoft Windows guests if the
 separate 'libguestfs-winsupport' package is not installed. If the
 guest is running Microsoft Windows, please try again after installing
 'libguestfs-winsupport'.
RHEL 7: Remove libguestfs live (RHBZ#798980).

This isn't supported in RHEL 7.
RHEL 7: Remove 9p APIs from RHEL (RHBZ#921710).
RHEL 7: Disable unsupported remote drive protocols (RHBZ#962113).

This disables support for unsupported remote drive protocols:

 * ftp
 * ftps
 * http
 * https
 * tftp
 * gluster
 * iscsi
 * rbd
 * sheepdog
 * ssh

Note 'nbd' is not disabled, and of course 'file' works.

We hope to gradually add some of these back over the lifetime of RHEL 7.
RHEL 7: Remove User-Mode Linux (RHBZ#1144197).

This isn't supported in RHEL 7.
RHEL 7: v2v: Select correct qemu binary for -o qemu mode (RHBZ#1147313).

RHEL 7 does not have qemu-system-x86_64 (etc), and in addition the
qemu binary is located in /usr/libexec.  Encode the path to this
binary directly in the script.

Note that we don't support people running qemu directly like this.
It's just for quick testing of converted VMs, and to help us with
support cases.
RHEL 7: v2v: Disable the --qemu-boot option (RHBZ#1147313).

This cannot work because there is no Gtk or SDL output mode
in RHEL 7's qemu-kvm.

In addition you will have to edit the -display option in the
qemu script.
RHEL 7: Revert "tests: rsync: Skip this test when the backend is libvirt."

This reverts commit 765dc6237ce7b93dd2f33d99be53eae92e048a7a.
RHEL 7: Revert "appliance: Change example ping lines to ping 8.8.8.8."

This reverts commit 07c0926b588db5c86214917b609c2f477c817c0e.
RHEL 7: Revert "launch: libvirt: Use qemu-bridge-helper to implement a full network (RHBZ#1148012)."

This reverts commit 224de20b9a8d5ea56f6337f19b4ca237bb88eca0.
RHEL 7: Revert "appliance: add dhcp-client on Mageia"

This reverts commit 8f3a2ca5358d5601be7a9247b6d08193c4e2da46.
RHEL 7: Revert "appliance: add dhcpcd and gptfdisk on Archlinux"

This reverts commit 979e7a49147f4ef1387337db262bf7ea12f627e3.
RHEL 7: Revert "appliance: Use dhclient or dhcpcd instead of hard-coding IP address of appliance."

This reverts commit 67e6f32a240c7c234e6af637c1cd324b36a82cd3.