[cloud] ec2_elb_facts fails on accounts with to many ELBs (#21602)

The list_elbs call to boto doesn't use any pagination, so any time there
are more ELBs than the API page size, this module will fail. This change
uses the `next_token` attribute of `ResultSet` to check if there are
still more ELBs to return.

Fixes #21361

lib/ansible/modules/cloud/amazon/ec2_elb_facts.py

@@ -78,6 +78,8 @@ EXAMPLES = '''
 
 '''
 
+import traceback
+
 try:
     import boto.ec2.elb
     from boto.ec2.tag import Tag
@@ -201,20 +203,28 @@ class ElbInformation(object):
 
 
     def list_elbs(self):
-        elb_array = []
-
-        try:
-            all_elbs = self.connection.get_all_load_balancers()
-        except BotoServerError as err:
-            self.module.fail_json(msg = "%s: %s" % (err.error_code, err.error_message))
+        elb_array, token = [], None
 
-        if all_elbs:
-            if self.names:
-                for existing_lb in all_elbs:
-                    if existing_lb.name in self.names:
-                        elb_array.append(existing_lb)
+        while True:
+            try:
+                all_elbs = self.connection.get_all_load_balancers(marker=token)
+                token = all_elbs.next_token
+            except BotoServerError as err:
+                self.module.fail_json(msg = "%s: %s" % (err.error_code, err.error_message),
+                    exception=traceback.format_exc())
+
+            if all_elbs:
+                if self.names:
+                    for existing_lb in all_elbs:
+                        if existing_lb.name in self.names:
+                            elb_array.append(existing_lb)
+                else:
+                    elb_array.extend(all_elbs)
             else:
-                elb_array = all_elbs
+                break
+
+            if token is None:
+                break
 
         return list(map(self._get_elb_info, elb_array))