SCTP: minor refactor

This patch adds some missing information in various debugging messages
which can help with debugging state-machine and connection-tracking.
It also renames some internal variable names for better code
readibility.

Change-Id: I68503fc0214300032f7514426c8b5b2b12edf11a
Signed-off-by: Marco Varlese <marco.varlese@suse.com>
diff --git a/src/vnet/sctp/sctp.h b/src/vnet/sctp/sctp.h
index 0d2e4b3..fd9d8da 100644
--- a/src/vnet/sctp/sctp.h
+++ b/src/vnet/sctp/sctp.h
@@ -524,13 +524,13 @@
 always_inline void
 sctp_half_open_connection_del (sctp_connection_t * tc)
 {
-  sctp_main_t *tm = vnet_get_sctp_main ();
-  clib_spinlock_lock_if_init (&tm->half_open_lock);
-  pool_put_index (tm->half_open_connections,
+  sctp_main_t *sctp_main = vnet_get_sctp_main ();
+  clib_spinlock_lock_if_init (&sctp_main->half_open_lock);
+  pool_put_index (sctp_main->half_open_connections,
 		  tc->sub_conn[MAIN_SCTP_SUB_CONN_IDX].c_c_index);
   if (CLIB_DEBUG)
     memset (tc, 0xFA, sizeof (*tc));
-  clib_spinlock_unlock_if_init (&tm->half_open_lock);
+  clib_spinlock_unlock_if_init (&sctp_main->half_open_lock);
 }
 
 always_inline u32