Fix deprecation warning.

BaseException.message is deprecated; if you have an exception of type
Exception (or subclass thereof), then "str(ex)" is the preferred way
to get the message.

Change-Id: I5b4acf88de538c1ef0f2db4fefaa92699937cd50
Fix swift_test_client duplicating request params

Remove extra lines of code that result in
swift_test_client adding params twice to
PUT request urls.

Bug was revealed while developing functional
tests for SLO - SLO manifest PUTs behave incorrectly
because the url constructed by swift_test_client ends
with ?multipart-manifest=put?multipart-manifest=put

Fixes bug 1248121

Change-Id: Ie5a8651a55049bb52ef641edfd6eb29b0ff3c245