SDOContextHelper in standalone/non-OSGi

While playing with Tuscany & SDO, I found an issue which to me looked like a bug in SDOContextHelper, in standalone/non-OSGi scenarios - unless I'm not getting it.

Without this patch, one of the test projects I wrote (available at https://github.com/vorburger/tuscany-sca-2.x/tree/trunk/samples/getting-started/helloworld-webservice-sdo-dynamic or https://github.com/vorburger/tuscany-sca-2.x/tree/trunk/samples/getting-started/helloworld-webservice-sdo) fail with a java.lang.NullPointerException at org.apache.tuscany.sca.databinding.sdo.ImportSDOProcessor.importWSDL(ImportSDOProcessor.java:176) - the proposed change address that.

Attached a proposed patch to SDOContextHelper. This should be reviewed by somebody with a better understanding of Tuscany's internals, SDO integration, and standalone SE/EE vs. OSGi environments.