Fix iosxr_config integration test failure (#44969)

*  Check for commands presence in case running config
   is used as base config for diff
*  Correct the fixtures

lib/ansible/modules/network/iosxr/iosxr_config.py

@@ -284,7 +284,7 @@ def run(module, result):
             commands = ['load harddisk:/ansible_config.txt']
             replace_file_path = 'harddisk:/ansible_config.txt'
 
-    if config_diff:
+    if config_diff or commands:
         if not replace_config:
             commands = config_diff.split('\n')
 

test/integration/targets/iosxr_config/fixtures/config_add_interface.txt

@@ -31,3 +31,5 @@ netconf-yang agent
 !
 ssh server v2
 ssh server netconf vrf default
+!
+end

test/integration/targets/iosxr_config/fixtures/config_del_interface.txt

@@ -25,3 +25,5 @@ netconf-yang agent
 !
 ssh server v2
 ssh server netconf vrf default
+!
+end