Make dhcp_leases simpler.
Make dhcp_leases simpler.

We do this by doing a lot more work in the wrapped
function, which allows us to get rid of some
additional error checking.

Signed-off-by: Chris Lalancette <281cd07d7578d97c83271fbbf2faddb83ab3791c@gmail.com>

libvirt/ruby-libvirt,libvirt/ruby-libvirt,libvirt/ruby-libvirt