Teiid Partial Results Mode: unavailability of datasource causes error (which is not masked)

Description of problem:
Querying a vdb-table which is formed as union of two tables from different datasources. Even though "set partialresultsmode true" is run as initial query, instead of retreiving 0 rows from a datasources that is down, exception is promoted.

Version-Release number of selected component (if applicable):
DV 6.1 ER1

How reproducible:
Every time

Steps to Reproduce:
1. Define one valid and one invalid datasource(invalid connection-url).
2. Create vdb which maps tables from both datasources.
3. Set partialresultsmode to true
4. Execute query on the given vdb-table

Actual results:
TeiidSQLException
TEIID30498 Remote org.teiid.api.exception.query.QueryPlannerException: TEIID30498 Capabilities for ORBQT were not avaialable. The command could not be planned properly.

Expected results:
0 rows from invalid datasource.