Don't bother creating thumbnails on non-desktop, at least for now

It seems that it was the thumbmail creation which through some
mechanism caused the blank tile problem for the first tile(s) for some
documents in TiledLibreOffice. Go figure.

Change-Id: I2b3d64e0bbd3bf39023c67aed56992048ea4ebcf
Add a couple SAL_INFOs

Change-Id: I3773f5432ff4e2a005e0c67d9c65fdb00de6f16b