Fix bugs that are not resources 'ReadStream' in AliOssAdapter.php

[wangyongdong]

There is a method bug in line 449in file ‘src/AliOssAdapter.php’.When I want to download the resource, the resource file type is judged incorrectly and should be compatible with the processing of the string.

[wangyongdong]

This is my modification. I did this for the first time. Please allow me to be curious.#56

[dmitryuk]

What differents with my older request https://github.com/jacobcyl/Aliyun-oss-storage/pull/54?

[farwish]

[fixed] rewind() need resource but string given, in readStream method