Don't assume buffered output echoes the command.

The if ((nlptr...)) implicitly assumes commptr != NULL (and that "buf"
starts with "cmd").  Make the assumption explicit, it will be broken in
a future patch.

* src/qemu_driver.c: Don't assume buffered monitor output echoes the
  command.

src/qemu_driver.c

@@ -2473,10 +2473,11 @@ qemudMonitorCommandExtra(const virDomainObjPtr vm,
                  * occurence, and inbetween the command and the newline starting
                  * the response
                  */
-                if ((commptr = strstr(buf, cmd)))
+                if ((commptr = strstr(buf, cmd))) {
                     memmove(buf, commptr, strlen(commptr)+1);
                     if ((nlptr = strchr(buf, '\n')))
                         memmove(buf+strlen(cmd), nlptr, strlen(nlptr)+1);
+                }
 
                 break;
             }