detect-engine: make output configurable (bug #2493)

[dbcfd]

Detect engine has a new rules analysis method that is outputting analysis as json to a file. This
output is not currently configurable, so checking existing config settings to see if rules analysis
should be output.

Make sure these boxes are signed before submitting your Pull Request -- thank you.

• I have read the contributing guide lines at https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Contributing
• I have signed the Open Information Security Foundation contribution agreement at https://suricata-ids.org/about/contribution-agreement/
• I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:

https://redmine.openinfosecfoundation.org/issues/2493https://redmine.openinfosecfoundation.org/issues/2493

Describe changes:

• Use config to determine if rules analysis should be output

PRScript output (if applicable):

[victorjulien]

QA fail