Include opt_ipsec.h so IPSEC/FAST_IPSEC is defined and the appropriate
code is compiled in to support the O_IPSEC operator. Previously no
support was included and ipsec rules were always matching. Note that
we do not return an error when an ipsec rule is added and the kernel
does not have IPsec support compiled in; this is done intentionally
but we may want to revisit this (document this in the man page).

PR: 58899
Submitted by: Bjoern A. Zeeb
Approved by: re (rwatson)