Goal: 

• os-net-config should support setting IPV6_FORCE_ACCEPT_RA and IPV6_SET_SYSCTLS in order to configure certain behavior with IPV6 that requires setting certain sysctl settings manually today. This will bring feature parity to NetworkManager which is able to configure IPV6 properly today.

This will involve code changes to os-net-config and documentation changes to show how to set the proper settings in ifcfg provider. If possible the same configuration options should be supported in nmstate provider, or ignored if they are not needed because the proper behavior already exists when other settings are configured.

Acceptance Criteria:

• Verify that when IPV6_SET_SYSCTLS is set the settings such as IPV6_FORCE_ACCEPT_RA and IPV6_AUTOCONF behave as expected
• Verify that the sysctl settings are set when the ifup script is run, and that the sysctls do not have to be set manually