libxl: disable VNC and SDL until explicitly enabled

When initializing a libxl_domain_build_info struct with
libxl_domain_build_info_init(), VNC is enabled by default.  As a
result, VMs configured with no graphics still have VNC enabled.
This behavior is a regression wrt to the legacy Xen driver.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

src/libxl/libxl_conf.c

@@ -745,6 +745,10 @@ libxlMakeDomBuildInfo(virDomainDefPtr def,
             return -1;
         }
 
+        /* Disable VNC and SDL until explicitly enabled */
+        libxl_defbool_set(&b_info->u.hvm.vnc.enable, 0);
+        libxl_defbool_set(&b_info->u.hvm.sdl.enable, 0);
+
         /*
          * The following comment and calculation were taken directly from
          * libxenlight's internal function libxl_get_required_shadow_memory():