Set maxAsgNamesPerDescribe to the new maximum value

While this was previously effectively limited to 50, `DescribeAutoScalingGroups` now supports
fetching 100 ASG per calls on all regions, matching what's documented:
https://docs.aws.amazon.com/autoscaling/ec2/APIReference/API_DescribeAutoScalingGroups.html
```
     AutoScalingGroupNames.member.N
       The names of the Auto Scaling groups.
       By default, you can only specify up to 50 names.
       You can optionally increase this limit using the MaxRecords parameter.
     MaxRecords
       The maximum number of items to return with this call.
       The default value is 50 and the maximum value is 100.
```

Doubling this halves API calls on large clusters, which should help to prevent throttling.

cluster-autoscaler/cloudprovider/aws/auto_scaling_test.go

@@ -27,22 +27,22 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestMoreThen50Groups(t *testing.T) {
+func TestMoreThen100Groups(t *testing.T) {
 	service := &AutoScalingMock{}
 	autoScalingWrapper := &autoScalingWrapper{
 		autoScaling: service,
 	}
 
-	// Generate 51 ASG names
-	names := make([]string, 51)
+	// Generate 101 ASG names
+	names := make([]string, 101)
 	for i := 0; i < len(names); i++ {
 		names[i] = fmt.Sprintf("asg-%d", i)
 	}
 
-	// First batch, first 50 elements
+	// First batch, first 100 elements
 	service.On("DescribeAutoScalingGroupsPages",
 		&autoscaling.DescribeAutoScalingGroupsInput{
-			AutoScalingGroupNames: aws.StringSlice(names[:50]),
+			AutoScalingGroupNames: aws.StringSlice(names[:100]),
 			MaxRecords:            aws.Int64(maxRecordsReturnedByAPI),
 		},
 		mock.AnythingOfType("func(*autoscaling.DescribeAutoScalingGroupsOutput, bool) bool"),
@@ -51,10 +51,10 @@ func TestMoreThen50Groups(t *testing.T) {
 		fn(testNamedDescribeAutoScalingGroupsOutput("asg-1", 1, "test-instance-id"), false)
 	}).Return(nil)
 
-	// Second batch, element 51
+	// Second batch, element 101
 	service.On("DescribeAutoScalingGroupsPages",
 		&autoscaling.DescribeAutoScalingGroupsInput{
-			AutoScalingGroupNames: aws.StringSlice([]string{"asg-50"}),
+			AutoScalingGroupNames: aws.StringSlice([]string{"asg-100"}),
 			MaxRecords:            aws.Int64(maxRecordsReturnedByAPI),
 		},
 		mock.AnythingOfType("func(*autoscaling.DescribeAutoScalingGroupsOutput, bool) bool"),

cluster-autoscaler/cloudprovider/aws/aws_manager.go

@@ -50,7 +50,7 @@ const (
 	operationWaitTimeout    = 5 * time.Second
 	operationPollInterval   = 100 * time.Millisecond
 	maxRecordsReturnedByAPI = 100
-	maxAsgNamesPerDescribe  = 50
+	maxAsgNamesPerDescribe  = 100
 	refreshInterval         = 1 * time.Minute
 	autoDiscovererTypeASG   = "asg"
 	asgAutoDiscovererKeyTag = "tag"