Remove the warning from RestController with Elasticsearch 5.5.1

[beihaifeiwu]

[2017-08-21T06:05:58,751][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:05:59,050][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:05:59,295][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:05:59,590][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:00,885][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:01,152][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:01,400][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:01,657][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:01,909][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.
[2017-08-21T06:06:02,121][WARN ][o.e.d.r.RestController   ] Content type detection for rest requests is deprecated. Specify the content type using the [Content-Type] header.