Strip out Traceback from HTTP response

We should not let stack traces leak to the REST API users

Fixes LP# 1103324
Fixes LP# 1092610

Change-Id: Ic1208bfeb7d44e672f8b8d3a4004a9802c14e7b9
Merge "Strip out Traceback from HTTP response"
Merge remote-tracking branch 'citrix/master' into build-temp