Re-vendor queue-worker publisher for reconnect

- re-vendor queue-worker for publisher via 0.6.0
- bump queue-worker version to 0.6.0 in docker-compose.yml for
AMD64
- use new naming for NATS of nats -> NATS in variables where
required
- add default reconnect of 60 times, 2 seconds apart.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

gateway/vendor/github.com/openfaas/nats-queue-worker/readconfig.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"log"
+	"os"
+	"strconv"
+	"time"
+)
+
+// ReadConfig constitutes config from env variables
+type ReadConfig struct {
+}
+
+func (ReadConfig) Read() QueueWorkerConfig {
+	cfg := QueueWorkerConfig{
+		AckWait:     time.Second * 30,
+		MaxInflight: 1,
+	}
+
+	if val, exists := os.LookupEnv("faas_nats_address"); exists {
+		cfg.NatsAddress = val
+	} else {
+		cfg.NatsAddress = "nats"
+	}
+
+	if val, exists := os.LookupEnv("faas_gateway_address"); exists {
+		cfg.GatewayAddress = val
+	} else {
+		cfg.GatewayAddress = "gateway"
+	}
+
+	if val, exists := os.LookupEnv("faas_function_suffix"); exists {
+		cfg.FunctionSuffix = val
+	}
+
+	if val, exists := os.LookupEnv("faas_print_body"); exists {
+		if val == "1" || val == "true" {
+			cfg.DebugPrintBody = true
+		} else {
+			cfg.DebugPrintBody = false
+		}
+	}
+
+	if val, exists := os.LookupEnv("write_debug"); exists {
+		if val == "1" || val == "true" {
+			cfg.WriteDebug = true
+		} else {
+			cfg.WriteDebug = false
+		}
+	}
+
+	if value, exists := os.LookupEnv("max_inflight"); exists {
+		val, err := strconv.Atoi(value)
+		if err != nil {
+			log.Println("max_inflight error:", err)
+		} else {
+			cfg.MaxInflight = val
+		}
+	}
+
+	if val, exists := os.LookupEnv("ack_wait"); exists {
+		ackWaitVal, durationErr := time.ParseDuration(val)
+		if durationErr != nil {
+			log.Println("ack_wait error:", durationErr)
+		} else {
+			cfg.AckWait = ackWaitVal
+		}
+	}
+
+	return cfg
+}
+
+type QueueWorkerConfig struct {
+	NatsAddress    string
+	GatewayAddress string
+	FunctionSuffix string
+	DebugPrintBody bool
+	WriteDebug     bool
+	MaxInflight    int
+	AckWait        time.Duration
+}