fix: fail2ban-regex with filter file failed

after merging #824, because test case missing;
test case for 'readexplicit' added;
@yarikoptic: please merge;
<blockquote>I would really prefer not to magically generate files upon 'read' command</blockquote>
What do you mean? 
It is a bug after merging #824 because we had no test cases for this method.
And this line is the solution for that, because DefinitionInitConfigReader(ConfigReader) is a wrapper now and SafeConfigParserWithIncludes.read needs a real implementation of config parser.