bgpd, ospfd, zebra: fix some DEFUN definitions

Fixup some DEFUNS with incorrect command strings or mixed up helpstrings.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/zebra/rtadv.c b/zebra/rtadv.c
index ae5c5a1..91d7b32 100644
--- a/zebra/rtadv.c
+++ b/zebra/rtadv.c
@@ -1483,7 +1483,7 @@
 
 ALIAS (no_ipv6_nd_router_preference,
        no_ipv6_nd_router_preference_val_cmd,
-       "no ipv6 nd router-preference (high|medium|low",
+       "no ipv6 nd router-preference (high|medium|low)",
        NO_STR
        "Interface IPv6 config commands\n"
        "Neighbor discovery\n"