[Libguestfs] v2v: Remove --no-trim, --vmtype options and other fixes.

[Richard W.M. Jones]

The first two patches implement the change discussed here:
https://www.redhat.com/archives/libguestfs/2016-April/msg00178.html

The third patch fixes the mapping of inspection data to OVF VmType
which was inherited directly from old virt-v2v and had never been
changed.  It had a number of problems.

The fourth patch is only slightly related to the others.  It adds an
extra slow test to ensure that trimming doesn't regress, fixing
https://bugzilla.redhat.com/show_bug.cgi?id=1264332

Rich.