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.
Also, we originally tried to do as you suggest (use PowerMock to stub the call and inject the return call), but we were having difficulties. I believe we had added the GlusterFileAttributes.class to the PrepareForTest annotation during our testing, but it's possible that we didn't. When we make the other changes, we'll definitely work on that and if we run into any problems, we'll address 'em then.