[libvirt] [PATCH] Don't clobber ID when redefining dom in xm driver

If redefining a domain in the xen xm driver, we unconditionally set the domain ID to -1. This can make a running domain appear inactive, and really confuse things. Just drop the offending code, since virGetDomain already sets the ID to -1 if required. Fix pointed out by Dan Berrange, more info can be found at https://bugzilla.redhat.com/show_bug.cgi?id=508278 Thanks, Cole