Removing TapeMode.DEFAULT since it doesn't really have a purpose, and defaulting to TapeMode.READ_ONLY instead.

Using a Groovy boolean expression on TapeMode.DEFAULT caused some unexpected logic, mostly revolving around constantly defaulting to TapeMode.READ_ONLY.

As a fix, I removed TapeMode.DEFAULT because it doesn't provide any real value, and defaulted to TapeMode.READ_ONLY.

Tests are fixed to use TapeMode.READ_WRITE where appropriate. IMO, better to be explicit when changing data than not.