Removed the need for preread_ifgs in check_correction_status
Removed the need for preread_ifgs in check_correction_status

The particular 'preread_ifg' required by this method was created specifically by a complicated protected function in process.py - this made it hard to test. There is nothin required by this function that a regular Ifg object doesn't provide.

GeoscienceAustralia/PyRate,GeoscienceAustralia/PyRate