BUG/MINOR: quic: Missing Initial packet dropping case

An Initial packet shorter than 1200 bytes must be dropped. The test was there
without the "goto drop"!

Must be backported to 2.6
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index c193c5f..e754d9e 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -5334,6 +5334,7 @@
 		         dgram->len < QUIC_INITIAL_PACKET_MINLEN) {
 			TRACE_PROTO("Too short datagram with an Initial packet", QUIC_EV_CONN_LPKT, qc);
 			HA_ATOMIC_INC(&prx_counters->too_short_initial_dgram);
+			goto drop;
 		}
 
 		/* When multiple QUIC packets are coalesced on the same UDP datagram,