(fix) Flush output stream before calling fd.sync, #480

[killme2008]

Motivation:

#480

Modification:

Flush output stream before calling FileDescriptor#sync in ProtoBufFile.save method. I also checked other code that do this stuff, they looks fine.

Result:

Fixes #480 .

It's a fatal issue, we should release a new version ASAP.

[killme2008]

@fengjiachun @zongtanghu 这个有空抓紧看下，需要发一个版本

[fengjiachun]

@fengjiachun @zongtanghu 这个有空抓紧看下，需要发一个版本

需要整理下代码缩进

[killme2008]

@fengjiachun 用了格式化命令了，会乱

[zongtanghu]

Maybe, it will be better that adding some unit test case? @killme2008

[killme2008]

@zongtanghu It's hard to test this case in unit test, because we can't mock system crash in java simply. I think we should verify it in chaos test.

[zongtanghu]

@zongtanghu It's hard to test this case in unit test, because we can't mock system crash in java simply. I think we should verify it in chaos test.

@killme2008 ok, it's nice!

[killme2008]

@fengjiachun It can be merged.