fix case in which file is created and backup is requested but fails, not it just…

fix case in which file is created and backup is requested but fails, not it just doesn't attempt to backup the missing file
Signed-off-by: Brian Coca <briancoca+ansible@gmail.com>

library/lineinfile

@@ -143,7 +143,7 @@ def present(module, dest, regexp, line, insertafter, create, backup):
         changed = True
 
     if changed:
-        if backup:
+        if backup and os.path.exists(dest):
             module.backup_local(dest)
         f = open(dest, 'wb')
         f.writelines(lines)