ospf6d: Add the missing ospf6 running check in show cmds

SYMPTOM:

If some of the ospfv3 commands like 'show ipv6 ospf6 route' are executed
with ospf6d daemon running but before having any ospfv3 configuration, then
ospf6d crash is seen.

ISSUE:

There are a few show commands, which are (unlike others) not checking if
ospf6 instance is initialized already.

FIX:

Add the missing checks, by using OSPF6_CMD_CHECK_RUNNING() in the commands
where its needed and not yet used.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
Reviewed-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
             Dinesh Dutt <ddutt@cumulusnetworks.com>
diff --git a/ospf6d/ospf6d.c b/ospf6d/ospf6d.c
index f9b0322..eae01af 100644
--- a/ospf6d/ospf6d.c
+++ b/ospf6d/ospf6d.c
@@ -1690,6 +1690,8 @@
   struct listnode *node;
   struct ospf6_area *oa;
 
+  OSPF6_CMD_CHECK_RUNNING ();
+
   for (ALL_LIST_ELEMENTS_RO (ospf6->area_list, node, oa))
     {
       vty_out (vty, "%s        SPF Result in Area %s%s%s",
@@ -1738,6 +1740,8 @@
   struct listnode *node;
   struct ospf6_area *oa;
 
+  OSPF6_CMD_CHECK_RUNNING ();
+
   /* copy argv to sargv and then append "detail" */
   for (i = 0; i < argc; i++)
     sargv[i] = argv[i];