rule-update: enable Suricata events rules if necessary

[dougburks]

If you run Setup and choose Snort, it disables the Suricata events rules. If you then switch from Snort to Suricata, those Suricata events rules are still disabled. rule-update needs to enable these rules if necessary.

[dougburks]

merged pull request:
Security-Onion-Solutions/securityonion-rule-update#7

submitted for testing:
https://groups.google.com/d/topic/security-onion-testing/Fr2oagl1FRI/discussion

[dougburks]

published:
http://blog.securityonion.net/2017/10/securityonion-rule-update-20151201.html