Sometimes write may be called twice in a row for the same content.

In a rare case it is possible that on write of a print document
adapter is called twice for the same pages with nothing being
changed. This happens if while doing a write we get an update
request which correctly avoids calling layout on the adapter
but does call on write as we ignore that we are waining for the
requested pages to be written. Fun.

Change-Id: I33d7d26c7c4b083dc7b66bf762697b6dafd1ccc4