Merge pull request #959 from jferlan/virsh_capabilities

virsh_capabilities: Find the qemu-kvm in os PATH
virsh_undefine: Move the fetching of uri

Move the fetching of the URI inside of remote code and place into
a try/except condition like other similar uses of code; otherwise,
when non remote code goes to run, the "-c 'uri'" is attached to the
virsh undefine command resulting in a need to provide authentication
credentials prior to each run.