Fix a virsh edit memory leak

Fix a virsh edit memory leak

When running virsh edit, we are unlinking and setting
the tmp variable to NULL before going to the end of the
function, meaning that we never free tmp.  Since the
exit to the function will always unlink and free tmp,
just remove this bit of code and let it get done at the
end.

Signed-off-by: Chris Lalancette <clalance@redhat.com>