[Libguestfs] [PATCH v6] v2v: Add -o rhv-upload output mode.

v5 was here: https://www.redhat.com/archives/libguestfs/2018-March/msg00032.html There is only a single patch in this version because the other patches went upstream. This patch adds the virt-v2v -o rhv-upload mode (https://bugzilla.redhat.com/show_bug.cgi?id=1557273). Compared to v5, this adds the ability to make zero, trim and flush requests to the oVirt imageio server (https://www.redhat.com/archives/libguestfs/2018-March/msg00119.html). However this is untested, although I believe it matches the specification (https://gerrit.ovirt.org/#/c/89022/). As a fallback it converts some zero requests into pwrites and ignores others, hopefully when it is safe to do so, and it doesn't make trim or flush requests at all. Also this adds the capability of setting the cluster. However it doesn't allow you to choose the datacenter yet. Also -of qcow2 probably doesn't work and is definitely not tested. Rich.