Necromance throttle in to the FreeNAS build.

(cherry picked from commit 072f12b08ce459fa9c32415c533302c20171bee0)

Ticket: #7188
Revert "throttle is no longer available."

This reverts commit 5a76c04af60039466005a43fcad73443434fa101.

(cherry picked from commit 5ec586939e20a2e8c8e866a2af7e1cf125c77865)

Ticket: #7188