qemu: Don't fail virDomainGetInfo if we can't update balloon info

Qemu driver tries to update balloon data in virDomainGetInfo and if it
can't do so because there is another monitor job running, it just
reports what's known in domain def. However, if there was no job running
but getting the data from qemu fails, we would fail the whole API. This
doesn't make sense. Let's make the failure nonfatal.

src/qemu/qemu_driver.c

@@ -2083,13 +2083,18 @@ static int qemudDomainGetInfo(virDomainPtr dom,
                 goto cleanup;
             }
 
-            if (err < 0)
-                goto cleanup;
-            if (err == 0)
+            if (err < 0) {
+                /* We couldn't get current memory allocation but that's not
+                 * a show stopper; we wouldn't get it if there was a job
+                 * active either
+                 */
+                info->memory = vm->def->mem.cur_balloon;
+            } else if (err == 0) {
                 /* Balloon not supported, so maxmem is always the allocation */
                 info->memory = vm->def->mem.max_balloon;
-            else
+            } else {
                 info->memory = balloon;
+            }
         } else {
             info->memory = vm->def->mem.cur_balloon;
         }