Update incorrect audit STIG rules for Ubuntu 18.04 STIG

[jgbradley1]

Pull Request (PR) description:

This PR updates several STIG rules for Canonical Ubuntu 18.04 LTS STIG (V2R7 and V2R8).

This fixes #1170. The list of STIG finding IDs impacted are:

V-219238
V-219239
V-219240
V-219241
V-219242
V-219243
V-219244
V-219245
V-219246
V-219247
V-219248
V-219249
V-219250
V-219251
V-219252
V-219253
V-219254
V-219255
V-219256
V-219257
V-219261
V-219262
V-219263
V-219264
V-219265
V-219266
V-219267
V-219268
V-219269
V-219270
V-219271
V-219272
V-219273
V-219274
V-219275
V-219276
V-219277
V-219279
V-219284
V-219285
V-219286
V-219287
V-219288
V-219289
V-219290
V-219293
V-219294
V-219295

Task list:

• Change details added to Unreleased section of CHANGELOG.md (Not required for Convert modules)?
• Added/updated documentation, comment-based help and descriptions where appropriate?

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This change is 

[jgbradley1]

There is another related problem with the Ubuntu STIG but I can create another PR if that would facilitate an easier review.

Issue: STIG policies state that all “audit” rules defined by a STIG finding should be defined in a file at /etc/audit/rules.d/stig.rules. PowerSTIG currently places those rules at /etc/audit/rules.d/audit.rules.

STIG compliance checkers do not seem to report the different filepath as being a problem. However it might be easier to maintain and debug if the audit rules are implemented exactly as stated by the STIG.

[erjenkin]

Parser update will be required to ensure future versions have the correct values

[erjenkin]

closing PR as update to parser has not been completed. Please reopen with parser updated