fixed onTask memory leak on PHP7.
fixed onTask memory leak on PHP7.

LinkedDestiny/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,tutanhamon/swoole-src,swoole/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,swoole/swoole-src,LinkedDestiny/swoole-src,swoole/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,swoole/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src,LinkedDestiny/swoole-src