JFR.stop misses the written info when the filename is only specified by JFR.start

```
$jcmd 87802 JFR.start name=test
87802:
Started recording 2. No limit specified, using maxsize=250MB as default.

Use jcmd 87802 JFR.dump name=test filename=FILEPATH to copy recording data to file.

$jcmd 87802 JFR.stop name=test filename=1.jfr
87802:
Stopped recording "test", 200.9 kB written to:

/home/denghui.ddh/my-jdk/1.jfr

$jcmd 87802 JFR.start name=test filename=2.jfr
87802:
Started recording 1. No limit specified, using maxsize=250MB as default.

Use jcmd 87802 JFR.dump name=test to copy recording data to file.

$jcmd 87802 JFR.stop name=test
87802:
Stopped recording "test".
```

The second 'JFR.stop' didn't print written info, but actually, 2.jfr was generated.