libxl: macro LOG() used in place of LIBXL__LOG in libxl_qmp.c

libxl: macro LOG() used in place of LIBXL__LOG in libxl_qmp.c

Code cleanup -- no functional changes

Coding style has recently been changed for libxl. The convenience macro
LOG() has been introduced, and it is intended that it calls to the old
macro LIBXL__LOG() be replaced with it. Change 7 occurences of the old
macro (in functions that have a local libxl_gc *gc) to the new one.

Signed-off-by: Kelley Nielsen <kelleynnn@gmail.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>