In previous commit c5f12e47e4 we changed
the PATH environment variable to run the locally built virt-v2v, not
the system-installed virt-v2v.
However this meant that we were running the locally built virt-v2v
against the system-installed libguestfs.so.0. We also need to set
LD_LIBRARY_PATH.
Fixes commit c5f12e47e4.