[Libguestfs] [PATCH] v2v: -o rhev: Don't break if image/metadata directory exists

As explained in the commit summary, if VDSM is going to create metadata and image directories, then virt-v2v should not mkdir those same directories (and hence fail). I'm not really convinced this is the right approach. I think instead of adding more and more hacks on top of '-o rhev' which should split this output mode into two sub modes, one for outputting to the RHEV Export Storage Domain (ie. "traditional" imports) and one which can handle the --rhev* parameters and the Data domain ('-o vdsm' perhaps?) Rich.