CA-141364: Don't ignore errors from libxc on domain build

Failures from these calls are fatal and we should not continue with any VM
build (start, resume) operations if these calls return an error.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
CA-141364: Remove redundant (and erroneous bindings)

We no longer need these bindings since this work is done in Xenguest. Also, it
appears both of the bindings mistakenly make the same call into libxc.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>