unix: exceptions in Serial::SerialImpl::reconfigurePort makes opened file descriptor hang in system.

[detorto]

If you try to create serial::Serial object, and something went wrong inreconfigurePortmethod (in my case - tcgetattr) - isOpened flag stays false, and ::close(_fd) method not called in destructor.
This makes opened descriptors hang, and in autodetection case, with full cycle over all available ports - exceeds the limits of opened fd's.

Probably, just need to remove if (is_open_ == true) condition in Serial::SerialImpl::close ()