server: always close http socket if responding with an error (issue6033) It's possible for hgweb to respond _very_ early with an error if we're catching certain types of errors. When we do, we need to tell the client the socket is toast when there's a POST involved because otherwise there can be lingering POST data on the socket that will confuse any future requests on the socket. This manifested as a flaky failure on Linux in an lfs extension test and a reliable failure on FreeBSD. With this patch applied, test-lfs-serve-access.t now passes for me on FreeBSD. Differential Revision: https://phab.mercurial-scm.org/D5498