sd/qa: Remove InteropGrabBag property from XML dumps

The InteropGrabBag property adds a lot of noise to this tests and it
doesn't actually have any purpose, because we are building their own
tests for InteropGrabBag-supported document attributes.

We have removed this property by default but we left a flag to enable
it when it's convenient for debugging.

Change-Id: I97cc7ba171783222a57ab5a96e5755070b949505