Refactored parseAttrs

Moved parseAttrs from GlusterFileChannel to GlusterFileAttributes. Made it a static method to enable its use in GFChannel. Modified the unit tests for GFAttributes and GFChannel to reflect this refactoring.
These comments are unnecessary & should be removed. Instead, use PowerMock to stub the call to GlusterFileAttributes.parseAttrs(attrs) and inject your mode, then later verify that the static method is called with attrs. Note: you will need to add GlusterFileAttributes.class to the PrepareForTest annotation at the top of the test class or else your verify will fail.