MB-25518 Add check to avoid panic if TLS_CONFIG is not set.
MB-25518 Add check to avoid panic if TLS_CONFIG is not set.

Change-Id: Ibc20fa24bb367f8be3407f17c02b10e9d3057c28
Reviewed-on: http://review.couchbase.org/84966
Well-Formed: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Tested-by: Isha Kandaswamy <e3cc845ebc6144fc4d71cf5f07a0ce9db6fdfa91@couchbase.com>

couchbase/cbauth,couchbase/cbauth