Closes #20: Fix Registration object update() method.

The method was checking if the supplied 'state' was 'bool' ... but it
should have been checking that the type(state) was 'bool'. This fixes
that, and adds just a bit of debug logging to make tracking this down in
the futur easier.

Change-Id: I2abc653b7bd87f5ee93e336faff9872c056c10ad