[Java][jersey2] set content-type as "application/octet-stream" in the request if not set

Created by: kevchentw

Before this fix, the content-type of the request defaults to "application/json".

With this fix, set it to "application/octet-stream"

It is not possible to not set any content-type to header, because jersey2 will raise the exception "java.lang.IllegalArgumentException: MediaType header is null"

relate to #8116 (closed), #10769, #10782

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