libxenguest: "standardize" LZO kernel decompression code

libxenguest: "standardize" LZO kernel decompression code

Add a DOMPRINTF() other methods have, indicating success. To facilitate
this, introduce an "outsize" local variable and update *size as well as
*blob only once done. The latter then also avoids leaving a pointer to
freed memory in dom->kernel_blob in case of a decompression error.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Wei Liu <wl@xen.org>
Release-Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>