HPCC-9154 Remove logging of daliUser usage

Currently there is logging code that logs the stack whenever daliuser
or NULL is specified as a user. This fix changes that logic to only
log when the user is NULL. Additionally this change allows the conditional
code to be built in by default, unless the _NO_DALIUSER_STACKTRACE flag
is specified

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>
Merge pull request #4246 from RussWhitehead/daliUser

HPCC-9154 Remove logging of daliUser usage

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>