fix: fail2ban-regex with filter file failed

after merging #824, because test case missing;
test case for 'readexplicit' added;
@yarikoptic: please merge;
aha, it is just that "touch(file)"  made me think that you are touching a missing file on the file system... I guess it is due to a bit unfortunate choice for the "touch" method name.  e.g. "create_unshared" would have been a bit more descriptive. Moreover it is really an implementation detail which I think might well even go into protected methods (i.e. become "_create_unshared")

What do you think?