Fixing newline escapes in lineinfile

Fixes #5679

files/lineinfile

@@ -18,6 +18,7 @@
 # You should have received a copy of the GNU General Public License
 # along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
 
+import pipes
 import re
 import os
 import tempfile
@@ -351,9 +352,14 @@ def main():
         if ins_bef is None and ins_aft is None:
             ins_aft = 'EOF'
 
-        # 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'])
+        # Replace escape sequences like '\n' while being sure 
+        # not to replace octal escape sequences (\ooo) since they
+        # match the backref syntax
+        if backrefs:
+            line = re.sub(r'(\\[0-9]{1,3})', r'\\\1', params['line'])
+        else:
+            line = params['line']
+        line = module.safe_eval(pipes.quote(line))
 
         present(module, dest, params['regexp'], line,
                 ins_aft, ins_bef, create, backup, backrefs)