CloudWatch: Add ALB RequestCountPerTarget metric

This commit adds the new ALB metric `RequestCountPerTarget` which was
released in July 2017.

pkg/tsdb/cloudwatch/metric_find_query.go

@@ -38,7 +38,7 @@ var customMetricsDimensionsMap map[string]map[string]map[string]*CustomMetricsCa
 func init() {
 	metricsMap = map[string][]string{
 		"AWS/ApiGateway":     {"4XXError", "5XXError", "CacheHitCount", "CacheMissCount", "Count", "IntegrationLatency", "Latency"},
-		"AWS/ApplicationELB": {"ActiveConnectionCount", "ClientTLSNegotiationErrorCount", "HealthyHostCount", "HTTPCode_ELB_4XX_Count", "HTTPCode_ELB_5XX_Count", "HTTPCode_Target_2XX_Count", "HTTPCode_Target_3XX_Count", "HTTPCode_Target_4XX_Count", "HTTPCode_Target_5XX_Count", "IPv6ProcessedBytes", "IPv6RequestCount", "NewConnectionCount", "ProcessedBytes", "RejectedConnectionCount", "RequestCount", "TargetConnectionErrorCount", "TargetResponseTime", "TargetTLSNegotiationErrorCount", "UnHealthyHostCount"},
+		"AWS/ApplicationELB": {"ActiveConnectionCount", "ClientTLSNegotiationErrorCount", "HealthyHostCount", "HTTPCode_ELB_4XX_Count", "HTTPCode_ELB_5XX_Count", "HTTPCode_Target_2XX_Count", "HTTPCode_Target_3XX_Count", "HTTPCode_Target_4XX_Count", "HTTPCode_Target_5XX_Count", "IPv6ProcessedBytes", "IPv6RequestCount", "NewConnectionCount", "ProcessedBytes", "RejectedConnectionCount", "RequestCount", "RequestCountPerTarget", "TargetConnectionErrorCount", "TargetResponseTime", "TargetTLSNegotiationErrorCount", "UnHealthyHostCount"},
 		"AWS/AutoScaling":    {"GroupMinSize", "GroupMaxSize", "GroupDesiredCapacity", "GroupInServiceInstances", "GroupPendingInstances", "GroupStandbyInstances", "GroupTerminatingInstances", "GroupTotalInstances"},
 		"AWS/Billing":        {"EstimatedCharges"},
 		"AWS/CloudFront":     {"Requests", "BytesDownloaded", "BytesUploaded", "TotalErrorRate", "4xxErrorRate", "5xxErrorRate"},