Cancel keepalive and lingering close on EOF better (ticket #2145).

Cancel keepalive and lingering close on EOF better (ticket #2145).

Unlike in 75e908236701, which added the logic to ngx_http_finalize_request(),
this change moves it to a more generic routine ngx_http_finalize_connection()
to cover cases when a request is finalized with NGX_DONE.

In particular, this fixes unwanted connection transition into the keepalive
state after receiving EOF while discarding request body.  With edge-triggered
event methods that means the connection will last for extra seconds as set in
the keepalive_timeout directive.