ospfd: compile warning cleanups

A set of patches to clarify some comments as well as cleanup code that was
causing warnings.  After these patches, the code can be compiled with

-Wall -Wsign-compare -Wpointer-arith -Wbad-function-cast -Wwrite-strings
-Wmissing-prototypes -Wmissing-declarations -Wchar-subscripts -Wcast-qual
-Wextra -Wno-unused-parameter -Wno-missing-field-initializers

(what is current in trunk plus -Wextra -Wno-unused-parameter
-Wno-missing-field-initializers).

Signed-off-by: Scott Feldman <sfeldma@cumulusnetworks.com>
diff --git a/ospfd/ospf_ism.c b/ospfd/ospf_ism.c
index db53882..fa7d97f 100644
--- a/ospfd/ospf_ism.c
+++ b/ospfd/ospf_ism.c
@@ -203,7 +203,6 @@
   struct in_addr old_dr, old_bdr;
   int old_state, new_state;
   struct list *el_list;
-  struct ospf_neighbor *dr, *bdr;
 
   /* backup current values. */
   old_dr = DR (oi);
@@ -216,8 +215,8 @@
   ospf_dr_eligible_routers (oi->nbrs, el_list);
 
   /* First election of DR and BDR. */
-  bdr = ospf_elect_bdr (oi, el_list);
-  dr = ospf_elect_dr (oi, el_list);
+  ospf_elect_bdr (oi, el_list);
+  ospf_elect_dr (oi, el_list);
 
   new_state = ospf_ism_state (oi);