Revert "Fix #5679 again after recent changes in core"

This reverts commit 2bfaacd170.

Fixes #6821

library/files/lineinfile

@@ -351,8 +351,9 @@ def main():
         if ins_bef is None and ins_aft is None:
             ins_aft = 'EOF'
 
-        # Replace the newline character with an actual newline.
-        line = params['line'].decode('string_escape')
+        # Replace the newline character with an actual newline. Don't replace
+		# escaped \\n, hence sub and not str.replace.
+        line = re.sub(r'\n', os.linesep, params['line'])
 
         present(module, dest, params['regexp'], line,
                 ins_aft, ins_bef, create, backup, backrefs)

test/integration/roles/test_lineinfile/tasks/main.yml

@@ -209,21 +209,3 @@
     that:
     - "result.stat.md5 == 'fef1d487711facfd7aa2c87d788c19d9'"
 
-
-- name: insert a multiple lines at the end of the file
-  lineinfile: dest={{output_dir}}/test.txt state=present line="This is a line\nwith \\\n character" insertafter="EOF"
-  register: result
-
-- name: assert that the multiple lines was inserted
-  assert:
-    that:
-    - "result.changed == true"
-    - "result.msg == 'line added'"
-
-- stat: path={{output_dir}}/test.txt
-  register: result
-
-- name: assert test md5 matches after insert the multiple lines
-  assert:
-    that:
-    - "result.stat.md5 == 'c2510d5bc8fdef8e752b8f8e74c784c2'"