fixing config read

[sherbacov]

Error:

[root@testzsnapd]# ./zsnapd-cfgtest
Traceback (most recent call last):
  File "./zsnapd-cfgtest", line 32, in <module>
    process.main()
  File "/usr/local/lib/python3.6/site-packages/magcode/core/process.py", line 419, in main
    self.main_process()
  File "/usr/share/zsnapd/zsnap/zsnapd_cfgtest.py", line 57, in main_process
    ds_settings = Config.read_ds_config()
  File "/usr/share/zsnapd/zsnap/config.py", line 409, in read_ds_config
    template_config = read_config(template_filename, template_dirname)
  File "/usr/share/zsnapd/zsnap/config.py", line 380, in read_config
    config.read(file_list)
UnboundLocalError: local variable 'file_list' referenced before assignment

If template.d extensions are not used, then when loading the configuration, an uninitialled variable is accessed.