pimd: Fix compile warning (error with Werror) on BSD

* ioctl commands can vary in type between systems, cast to an unsigned long
  before passing to format command.
diff --git a/pimd/pim_cmd.c b/pimd/pim_cmd.c
index 55545c1..880edb9 100644
--- a/pimd/pim_cmd.c
+++ b/pimd/pim_cmd.c
@@ -2344,8 +2344,11 @@
     if (ioctl(qpim_mroute_socket_fd, SIOCGETSGCNT, &sgreq)) {
       int e = errno;
       vty_out(vty,
-         "ioctl(SIOCGETSGCNT=%d) failure for (S,G)=(%s,%s): errno=%d: %s%s",
-         SIOCGETSGCNT,
+         "ioctl(SIOCGETSGCNT=%lu) failure for (S,G)=(%s,%s): errno=%d: %s%s",
+         /* note that typeof ioctl defs can vary across platforms, from
+          * int, to unsigned int, to long unsigned int
+          */
+         (unsigned long)SIOCGETSGCNT,
          source_str,
          group_str,
          e,