net/quagga: unbreak ripd for 1.2.4

ripd is essentially non-functional in quagga-1.2.4
as it aborts on first announce timeout due to some threading logic bug.

The problem was reported upstream over a year ago and ignored:
https://bugzilla.quagga.net/show_bug.cgi?id=985
https://bugzilla.quagga.net/show_bug.cgi?id=1008

Add work-around that restores ripd stability.

PR: 238760
Approved by: pi (maintainer timeout, 2 weeks)