fixes bug with junos_config module not properly loading config (#5213)

This fixes two issues.  First, it fixes an issue with the junos_config
module not properly recognizing a file with set commands.  The second
bug would cause the diff_config() function to raise an exception due
to a blank line when splitting the config

lib/ansible/modules/network/junos/junos_config.py

@@ -217,18 +217,19 @@ def diff_commands(commands, config):
     updates = list()
     visited = set()
 
-    for item in commands:
-        if not item.startswith('set') and not item.startswith('delete'):
-            raise ValueError('line must start with either `set` or `delete`')
-
-        elif item.startswith('set') and item[4:] not in config:
-            updates.append(item)
-
-        elif item.startswith('delete'):
-            for entry in config:
-                if entry.startswith(item[7:]) and item not in visited:
-                    updates.append(item)
-                    visited.add(item)
+    for item in commands.split('\n'):
+        if len(item) > 0:
+            if not item.startswith('set') and not item.startswith('delete'):
+                raise ValueError('line must start with either `set` or `delete`')
+
+            elif item.startswith('set') and item[4:] not in config:
+                updates.append(item)
+
+            elif item.startswith('delete'):
+                for entry in config:
+                    if entry.startswith(item[7:]) and item not in visited:
+                        updates.append(item)
+                        visited.add(item)
 
     return updates