daemon: Implement set-label for XFS and fix it for btrfs (RHBZ#986875).

Implement 'set-label' for XFS filesystems.

Fix the call for btrfs.  Previous
commit d5817537fa6c51a7f851ecc5e4e63e60609e0c03 added some bogus
documentation implying this call would work for btrfs, but it did
not.

Add tests.

(cherry picked from commit 091d22f49e7fcb53fb3bb23e2ba94ca12eb88eab)
New API: Implement set-uuid for ext2/3/4 and XFS (RHBZ#986877).

Also includes tests.

(cherry picked from commit 8580ef7d0f2aac2118fa7b4055f3eb28cd127093)
docs: Document labels and UUIDs in the API overview section.

(cherry picked from commit df02c2471f3fe94c691c389c17a5d23d052848dd)
sysprep: Add new fs-uuids operation.

This creates new random UUIDs for all filesystems in a guest.

Cherry picked from commit 8965368eb89532ac1613fffb0a3a661f005bae81
and modified for virt-sysprep in libguestfs 1.22.
sysprep: Disable fs-uuids operation by default.

Disable this operation because it is more likely than not to break
Linux guests.

To fix this properly will involve finding all the places in the guest
where the UUIDs are used to locate and mount filesystems,
eg. /etc/fstab and possibly initramfs.

This updates commit 8965368eb89532ac1613fffb0a3a661f005bae81.

(cherry picked from commit 5deea7fce675edb6803cd83a699b80e8ea383488)
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: Exclude iptables from the appliance (RHBZ#858648).
RHEL 7: Ignore /etc/release if /etc/redhat-release exists (RHBZ#873219).

If the user has created /etc/release on a RHEL machine, don't
mis-detect the OS as NetBSD.
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.