libxl: vz: Use accessor instead of direct access for max_balloon

Commits 45697fe5 and f863ac80 used direct access to the variable instead
of the preferred accessor method.

src/libxl/libxl_driver.c

@@ -553,7 +553,7 @@ libxlAddDom0(libxlDriverPrivatePtr driver)
     vm->def->vcpus = d_info.vcpu_online;
     vm->def->maxvcpus = d_info.vcpu_max_id + 1;
     vm->def->mem.cur_balloon = d_info.current_memkb;
-    vm->def->mem.max_balloon = d_info.max_memkb;
+    virDomainDefSetMemoryInitial(vm->def, d_info.max_memkb);
 
     ret = 0;
 

src/vz/vz_driver.c

@@ -1200,7 +1200,7 @@ vzDomainGetMaxMemory(virDomainPtr domain)
     if (!(dom = vzDomObjFromDomain(domain)))
         return -1;
 
-    ret = dom->def->mem.max_balloon;
+    ret = virDomainDefGetMemoryActual(dom->def);
     virObjectUnlock(dom);
     return ret;
 }