qemu: Fix memory leak in qemuProcessWaitForMonitor

Move "VIR_FREE(buf) into label "closelog", so that "buf" could be
freed before returning.

src/qemu/qemu_process.c

@@ -1122,9 +1122,9 @@ cleanup:
         ret = -1;
     }
 
+closelog:
     VIR_FREE(buf);
 
-closelog:
     if (VIR_CLOSE(logfd) < 0) {
         char ebuf[1024];
         VIR_WARN("Unable to close logfile: %s",