THRIFT-5324: Create new req buffer for every http request
THRIFT-5324: Create new req buffer for every http request

Client: go

The fix in https://github.com/apache/thrift/pull/2293 doesn't work for
go1.10.8 due to the possibility of data races. This exposes a bigger,
underlying issue regarding the ownership of the request buffer in
THttpClient between THttpClient itself and the http request it creates.
Instead of reset and reuse the same buffer, always give up the ownership
of it and create a new buffer after each Flush call.

yongju-hong/thrift,strava/thrift,apache/thrift,yongju-hong/thrift,strava/thrift,bforbis/thrift,nsuke/thrift,apache/thrift,yongju-hong/thrift,yongju-hong/thrift,jeking3/thrift,jeking3/thrift,apache/thrift,strava/thrift,Jens-G/thrift,yongju-hong/thrift,bforbis/thrift,nsuke/thrift,bforbis/thrift,yongju-hong/thrift,yongju-hong/thrift,apache/thrift,jeking3/thrift,strava/thrift,Jens-G/thrift,bforbis/thrift,bforbis/thrift,yongju-hong/thrift,apache/thrift,apache/thrift,yongju-hong/thrift,apache/thrift,bforbis/thrift,apache/thrift,strava/thrift,yongju-hong/thrift,Jens-G/thrift,bforbis/thrift,Jens-G/thrift,Jens-G/thrift,yongju-hong/thrift,apache/thrift,nsuke/thrift,yongju-hong/thrift,yongju-hong/thrift,yongju-hong/thrift,jeking3/thrift,strava/thrift,Jens-G/thrift,Jens-G/thrift,jeking3/thrift,apache/thrift,Jens-G/thrift,bforbis/thrift,jeking3/thrift,strava/thrift,jeking3/thrift,nsuke/thrift,strava/thrift,strava/thrift,jeking3/thrift,nsuke/thrift,jeking3/thrift,jeking3/thrift,nsuke/thrift,jeking3/thrift,strava/thrift,apache/thrift,nsuke/thrift,Jens-G/thrift,jeking3/thrift,apache/thrift,jeking3/thrift,strava/thrift,yongju-hong/thrift,nsuke/thrift,bforbis/thrift,Jens-G/thrift,nsuke/thrift,strava/thrift,bforbis/thrift,bforbis/thrift,apache/thrift,Jens-G/thrift,apache/thrift,nsuke/thrift,bforbis/thrift,apache/thrift,Jens-G/thrift,bforbis/thrift,nsuke/thrift,apache/thrift,nsuke/thrift,apache/thrift,apache/thrift,strava/thrift,jeking3/thrift,jeking3/thrift,Jens-G/thrift,Jens-G/thrift,strava/thrift,strava/thrift,bforbis/thrift,Jens-G/thrift,bforbis/thrift,Jens-G/thrift,bforbis/thrift,nsuke/thrift,nsuke/thrift,Jens-G/thrift,strava/thrift,yongju-hong/thrift,yongju-hong/thrift,strava/thrift,nsuke/thrift,Jens-G/thrift,nsuke/thrift,nsuke/thrift,bforbis/thrift,jeking3/thrift