fix grub2_argument bash remediation

[vojtapolasek]

Description:

Fixed the bash remediation for grub2_argument template by removing "audit=1" and replacing it with proper Jinja macro.

Also wrote tests for the grub2_pti_argument rule.

Rationale:

It was found that in the Bash remediation for the grub2_argument template specifically for rhel8, there was hardcoded "audit=1" instead of proper Jinja macro. This caused wrong remediations for templated rules other than grub2_audit_argument.

[yuumasato]

@vojtapolasek Thank you for looking into this!

Test scenarios are passing:

$ python3 test_suite.py rule --libvirt qemu:///session rhel8.1-snap --profile ospp --datastream ../build/ssg-rhel8-ds.xml --debug grub2_audit_argument
Setting console output to log level INFO
INFO - The base image option has not been specified, choosing libvirt-based test environment.
INFO - Logging into /home/wsato/git/content/tests/logs/rule-custom-2019-10-03-1445/test_suite.log
INFO - xccdf_org.ssgproject.content_rule_grub2_audit_argument
WARNING - Script wrong_value_rhel7.fail.sh is not applicable on given platform
WARNING - Script correct_grubby.pass.sh is not applicable on given platform
WARNING - Script arg_not_there_etcdefaultgrub_recovery_disabled.fail.sh is not applicable on given platform
WARNING - Script wrong_value_etcdefaultgrub_recovery_disabled.fail.sh is not applicable on given platform
WARNING - Script correct_recovery_disabled.pass.sh is not applicable on given platform
WARNING - Script arg_not_there_rhel7.fail.sh is not applicable on given platform
WARNING - Script wrong_value_etcdefaultgrub.fail.sh is not applicable on given platform
WARNING - Script arg_not_there_etcdefaultgrub.fail.sh is not applicable on given platform
INFO - Script wrong_value_rhel8.fail.sh using profile xccdf_org.ssgproject.content_profile_ospp OK
INFO - Script arg_not_there_rhel8.fail.sh using profile xccdf_org.ssgproject.content_profile_ospp OK
INFO - Script correct_value.pass.sh using profile xccdf_org.ssgproject.content_profile_ospp OK
INFO - Script correct_grubenv.pass.sh using profile xccdf_org.ssgproject.content_profile_ospp OK

$ python3 test_suite.py rule --libvirt qemu:///session rhel8.1-snap --profile ospp --datastream ../build/ssg-rhel8-ds.xml --debug grub2_pti_argument
Setting console output to log level INFO
INFO - The base image option has not been specified, choosing libvirt-based test environment.
INFO - Logging into /home/wsato/git/content/tests/logs/rule-custom-2019-10-03-1448/test_suite.log
INFO - xccdf_org.ssgproject.content_rule_grub2_pti_argument
INFO - Script correct.pass.sh using profile xccdf_org.ssgproject.content_profile_ospp OK
INFO - Script arg_not_there.fail.sh using profile xccdf_org.ssgproject.content_profile_ospp OK
INFO - Script wrong_value.fail.sh using profile xccdf_org.ssgproject.content_profile_ospp OK