Add assertion on test_iosxr_facts (#23852)

We hit bug #23737 due to bad coverage on test_iosxr_facts, we
were not checking memory facts at all.
(cherry picked from commit 60de93c31d)

test/units/modules/network/iosxr/test_iosxr_facts.py

@@ -68,6 +68,8 @@ class TestIosxrFacts(TestIosxrModule):
         self.assertEquals(['disk0:', 'flash0:'], ansible_facts['ansible_net_filesystems'])
         self.assertIn('GigabitEthernet0/0/0/0',
             ansible_facts['ansible_net_interfaces'].keys())
+        self.assertEquals('3095', ansible_facts['ansible_net_memtotal_mb'])
+        self.assertEquals('1499', ansible_facts['ansible_net_memfree_mb'])
 
     def test_iosxr_facts_gather_subset_config(self):
         set_module_args({'gather_subset': 'config'})