bgpd, zebra: fix struct/pointer sizeof mixups

Two places were taking sizeof(pointer) instead of the sizeof(struct),
while performing operations on the struct.  Both are initialisation
functions;  I guess we haven't seen fallout since they weren't critical.
Fix anyway.

[v2: fix mistake that actually broke bgpd RS workqueue init]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
(cherry picked from commit d43f8b39b075fe60e0c8fdb33b07b284d3fae503)