HTTP/2: backed out 16905ecbb49e (ticket #822).

HTTP/2: backed out 16905ecbb49e (ticket #822).

It caused inconsistency between setting "in_closed" flag and the moment when
the last DATA frame was actually read.  As a result, the body buffer might not
be initialized properly in ngx_http_v2_init_request_body(), which led to a
segmentation fault in ngx_http_v2_state_read_data().  Also it might cause
start processing of incomplete body.

This issue could be triggered when the processing of a request was delayed,
e.g. in the limit_req or auth_request modules.