Restore compatibility with PrettyTable < 0.7.2

PrettyTable 0.7.2 defaults to print a table even if
the resultset is empty. Restore previous behavior
to be in line with older prettytable releases.

Change-Id: Idd1d0c2c2f41966076517cbc8819ba9a5e097306
Added Conflict Exception to the exception code map

The Conflict Exception is added for HTTP error code 409.
However this exception is never raised as this class is not added to
the error_code map and always raises the ClientException whenever a
409 code is returned.

Fixes bug #1168826

Change-Id: I7045eae33533ff603f4aab61ea988264b46f0d09
Merge "Restore compatibility with PrettyTable < 0.7.2"
Merge "Added Conflict Exception to the exception code map"