isisd: address Coverity warnings

this fixes a bunch of issues found by Coverity SCAN and flagged as
"high" impact -- although, they're all rather minute issues.

* isisd/isis_adjacency.c: one superfluous check, one possible NULL deref
* isisd/isis_circuit.c: two prefix memory leaks
* isisd/isis_csm.c: one missing break
* isisd/isis_lsp.c: one possible NULL deref
* isisd/isis_pfpacket.c: one error-case fd leak
* isisd/isis_route.c: one isis_route_info memory leak
* isisd/isis_routemap.c: one... fnord
* isisd/isis_tlv.c: one infinite loop

Reported-by: Coverity SCAN
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/isisd/isis_spf.c b/isisd/isis_spf.c
index 1cb5113..e0a8d01 100644
--- a/isisd/isis_spf.c
+++ b/isisd/isis_spf.c
@@ -1492,7 +1492,7 @@
   struct listnode *anode;
   struct isis_vertex *vertex;
   struct isis_adjacency *adj;
-  u_char buff[255];
+  u_char buff[BUFSIZ];
 
   vty_out (vty, "Vertex               Type         Metric "
                 "Next-Hop             Interface Parent%s", VTY_NEWLINE);