MINOR: quic: Add missing traces in cubic algorithm implementation

May be useful to debug.

Must be backported to 2.7 and 2.6.
diff --git a/src/quic_cc_cubic.c b/src/quic_cc_cubic.c
index e91b766..e04cd3e 100644
--- a/src/quic_cc_cubic.c
+++ b/src/quic_cc_cubic.c
@@ -38,6 +38,7 @@
 {
 	struct cubic *c = quic_cc_priv(cc);
 
+	TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
 	cc->algo->state = QUIC_CC_ST_SS;
 
 	c->ssthresh = QUIC_CC_INFINITE_SSTHESH;
@@ -49,6 +50,7 @@
 	c->last_w_max = 0;
 	c->tcp_wnd = 0;
 	c->recovery_start_time = 0;
+	TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
 }
 
 static int quic_cc_cubic_init(struct quic_cc *cc)
@@ -100,6 +102,7 @@
 	uint32_t t, target, inc, inc_diff;
 	uint64_t delta, diff;
 
+	TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
 	if (!c->epoch_start) {
 		c->epoch_start = now_ms;
 		if (c->last_w_max <= path->cwnd) {
@@ -133,7 +136,7 @@
 		 * control algorithm reset.
 		 */
 		quic_cc_cubic_reset(cc);
-		return;
+		goto leave;
 	}
 
 	delta = path->mtu * ((CUBIC_C * diff * diff * diff) >> (10 + 3 * TIME_SCALE_FACTOR_SHIFT));
@@ -165,11 +168,15 @@
 	}
 
 	path->cwnd += inc;
+ leave:
+	TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
 }
 
 static void quic_cc_cubic_slow_start(struct quic_cc *cc)
 {
+	TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
 	quic_cc_cubic_reset(cc);
+	TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc);
 }
 
 static void quic_enter_recovery(struct quic_cc *cc)
@@ -178,6 +185,7 @@
 	struct cubic *c = quic_cc_priv(cc);
 	/* Current cwnd as number of packets */
 
+	TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc);
 	c->epoch_start = 0;
 	c->recovery_start_time = now_ms;
 	/* Fast convergence */
@@ -191,6 +199,7 @@
 	path->cwnd = (CUBIC_BETA * path->cwnd) >> CUBIC_BETA_SCALE_SHIFT;
 	c->ssthresh =  QUIC_MAX(path->cwnd, path->min_cwnd);
 	cc->algo->state = QUIC_CC_ST_RP;
+	TRACE_LEAVE(QUIC_EV_CONN_CC, cc->qc, NULL, cc);
 }
 
 /* Congestion slow-start callback. */
@@ -252,7 +261,7 @@
 	struct cubic *c = quic_cc_priv(cc);
 
 	TRACE_ENTER(QUIC_EV_CONN_CC, cc->qc, ev);
-	TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev);
+	TRACE_PROTO("CC cubic", QUIC_EV_CONN_CC, cc->qc, ev, cc);
 
 	BUG_ON(!tick_isset(c->recovery_start_time));