[RHEL/7][Fedora] Update IPv6 Kernel Module to sysctl setting

- Migrate IPv6 kernel module disable to sysctl settings
- Enabled for Fedora
- Fixes #60
[RHEL/7] add Sysctl IPv6 Kernel check
[shared] Fix remediation script for 'Set Deny For Failed Password Attempts' issue wrt to
         problems noted in issue #304.
[shared] Fix indentation for accounts_passwords_pam_faillock_deny remediation script yet
         (so it would align with other rows in /etc/pam.d/{password,system}-auth files)
Merge pull request #305 from iankko/shared_fix_accounts_passwords_pam_faillock_deny_remediation

[bugfix] [shared] Fix remediation script for 'Set Deny For Failed Password Attempts wrt to issue #304
Merge pull request #300 from redhatrises/kernel_ipv6_sysctl

[RHEL/7][Fedora] Update IPv6 Kernel Module to sysctl setting