http/h1_stream: handle EOF when body_read_type==length

If a client closes the connection before sending the expected number of bytes
then return `EPIPE`.
This fixes a potential infinite draining loop when trying to trying to
`:shutdown()` a stream.

http/h1_stream.lua

@@ -861,6 +861,8 @@ function stream_methods:read_next_chunk(timeout)
 			if chunk ~= nil then
 				self.body_read_left = length_n - #chunk
 				end_stream = (self.body_read_left == 0)
+			elseif err == nil then
+				return nil, ce.strerror(ce.EPIPE), ce.EPIPE
 			end
 		elseif length_n == 0 then
 			chunk = ""

spec/h1_stream_spec.lua

@@ -295,6 +295,33 @@ describe("http1 stream", function()
 		server:close()
 		client:close()
 	end)
+	it("Doesn't hang when a content-length delimited stream is closed", function()
+		local server, client = new_pair(1.1)
+		local cq = cqueues.new()
+		cq:wrap(function()
+			local stream = client:new_stream()
+			local headers = new_headers()
+			headers:append(":method", "GET")
+			headers:append(":scheme", "http")
+			headers:append(":authority", "myauthority")
+			headers:append(":path", "/a")
+			assert(stream:write_headers(headers, true))
+		end)
+		cq:wrap(function()
+			local stream = server:get_next_incoming_stream()
+			assert(stream:get_headers())
+			local res_headers = new_headers()
+			res_headers:append(":status", "200")
+			res_headers:append("content-length", "100")
+			assert(stream:write_headers(res_headers, false))
+			assert(stream:write_chunk("foo", false))
+			assert(stream:shutdown())
+		end)
+		assert_loop(cq, TEST_TIMEOUT)
+		assert.truthy(cq:empty())
+		server:close()
+		client:close()
+	end)
 	it("allows pipelining", function()
 		local server, client = new_pair(1.1)
 		local cq = cqueues.new()