(FACT-592) Unbreak swapfree/swapsize facts on OpenBSD

On OpenBSD the "swapctl -s" output also reports the blocksize which
must be taken into account. Also the scaler was incorrectly reporting
terabytes of swap instead of gigabytes.

The spec tests were updated accordingly which were passing, eventhough they didn't quite match the actual output of `swapctl -s` on a real system.