sctp: Fix the SNMP number of SCTP_MIB_CURRESTAB

RFC3873 defined SCTP_MIB_CURRESTAB:
sctpCurrEstab OBJECT-TYPE

    SYNTAX         Gauge32
    MAX-ACCESS     read-only
    STATUS         current

DESCRIPTION
"The number of associations for which the current state is either ESTABLISHED, SHUTDOWN-RECEIVED or SHUTDOWN-PENDING."
REFERENCE
"Section 4 in RFC2960 covers the SCTP Association state
diagram."

If the T4 RTO timer expires many times(timeout), the association will enter CLOSED state, so we should dec the number of SCTP_MIB_CURRESTAB, not inc the number of SCTP_MIB_CURRESTAB.

---
 net/sctp/sm_statefuns.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

index 7c622af..82c77b4 100644
@@ -5432,7 +5432,7 @@ sctp_disposition_t sctp_sf_t4_timer_expire(
 		sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
 				SCTP_PERR(SCTP_ERROR_NO_ERROR));
 		SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
-		SCTP_INC_STATS(SCTP_MIB_CURRESTAB);
+		SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
 		return SCTP_DISPOSITION_ABORT;
 	}
 

1.5.3.8