MINOR: httpclient: set HTTPCLIENT_F_ENDED only in release

Only set the HTTPCLIENT_F_ENDED flag in httpclient_applet_release()
function so we are sure that the appctx is not used anymore once the
flag is set.
diff --git a/src/http_client.c b/src/http_client.c
index 9e5b2e8..3ea86c2 100644
--- a/src/http_client.c
+++ b/src/http_client.c
@@ -578,7 +578,6 @@
 					 * set, leave (no body) */
 					if (htx_is_empty(htx) && htx->flags & HTX_FL_EOM) {
 						appctx->st0 = HTTPCLIENT_S_RES_END;
-						hc->flags |= HTTPCLIENT_F_ENDED;
 					} else {
 						appctx->st0 = HTTPCLIENT_S_RES_BODY;
 					}