Fixes for regressions in Unit Tests for sbt and sbtx projects.

1. Changed the service implementation for calling notifyError method. It
has been moved from validate.js to util.js
2. Added an additional check in endpoint.js to verify whether message
field in the error object is present before constructing the error
message in endpoint.js

Executed sbtTestSuite and sbtxTestSuite with dojo180, dojo143 and
jquery180 to verify no regressions.