rtsold: run script if MANAGED bit set

[emes]

• [ x ] Redmine Issue: https://redmine.pfsense.org/issues/10965
• [ x ] Ready for review

In FreeBSD 12.2-STABLE rtsold was changed to allow for a script to run when the router advertisement has the MANAGED flag set.

From rfc4861:

M              1-bit "Managed address configuration" flag.  When
                      set, it indicates that addresses are available via
                      Dynamic Host Configuration Protocol [DHCPv6].
 
                      If the M flag is set, the O flag is redundant and
                      can be ignored because DHCPv6 will return all
                      available configuration information.

If the managed bit is set then the script specified with the -O option is not executed. The -M option is (currently) processed before the -O option. The {$g['varetc_path']}/rtsold_{$wanif}_script.sh never runs and therefore no DHCPv6 client is started.

I probably could have just changed the O option to M, but seemed safer and possibly more resistant to future rtsold changes to include both since only one will execute.

rtsold.c changes:

freebsd/freebsd-src@8ffcd47

https://reviews.freebsd.org/D26099

I also noticed that the {$g['varetc_path']}/rtsold_{$wanif}_script.sh is using $2 when the input to the script is only the name of the interface, but did not address that.