[Libvirt-cim] Various fixes revealed by Coverity scan report

Hi all, The cool RedHat folks were kind enough to share a recent report generated by Coverity which exposes a lot of potential errors on libvirt-cim code. https://bugzilla.redhat.com/show_bug.cgi?id=728245#c8 https://bugzilla.redhat.com/attachment.cgi?id=530435 I went through each one of them and fixed all of them that I considered it actually make sense to fix. There are a few false positives that were ignored. The result is this series of patches following. Finally, I have ran the cimtests with all these applied and they work as expected. Best regards, -- Eduardo de Barros Lima Software Engineer, Open Virtualization Linux Technology Center - IBM/Brazil eblima(a)br.ibm.com