testeth crashes at the end

When using test filter with `*` the testeth will crash. E.g. 
```
terminate called after throwing an instance of 'boost::filesystem::filesystem_error'
  what():  boost::filesystem::directory_iterator::construct: No such file or directory: "/home/chfast/Projects/ethereum/aleth/test/jsontests/src/GeneralStateTestsFiller/*"
[1]    24270 abort (core dumped)  testeth -t 'GeneralStateTests/*'
```