[PR] Sling Engine: add unit tests for TRACE-disabled handling and selector validation

[aswin dhanan]

Hi all,

I opened a small PR adding unit test coverage in
sling-org-apache-sling-engine for TRACE-disabled handling and selector
validation.

PR: https://github.com/apache/sling-org-apache-sling-engine/pull/70

This is my first contribution to Sling; feedback is very welcome.

Thanks,
Aswin