Cleanup trace generated for Exodus reader.

Exodus reader was generating unnecessary entries in the trace file. This was
because the XML was setting a default number of values count for server
properties which wasnt needed. Fixed that.

Also fixed vtkSMVectorPropertyTemplate to fire modified event in SetElements(..)
for uninitialized properties only when the new value had a non-zero number of
elements.

Change-Id: Iab759d282e80e7818c67dbf8a002e8a37167b729
Merge topic '0014214_fix_python_trace_issues' into next

f5e284d Cleanup trace generated for Exodus reader.