Fixes client to send 0 for min/max size

Previously, if 0 is passed as the min_size or max_size for a
configuration, the Trove client would ignore it and not put it in the
dict making up the request body. This changes that code to explicitly
check if this value is not None instead of ignoring it if its zero.

Co-Authored-By: Craig Vyvial <cp16net@gmail.com>

Fixes bug: 1398995

Change-Id: I7f1d196b00a612365576bfb82fbfd35d647588d4