ns2: nsvc: reject UNITDATA  when the remote BLOCK'ed

When the remote initiated the BLOCK the nsvc would still accept UNITDATA
over this nsvc.

Change-Id: I3ed4aa105a84e448082d3028fe844aae7720426b
diff --git a/src/gb/gprs_ns2_vc_fsm.c b/src/gb/gprs_ns2_vc_fsm.c
index 1fcc3ad..7649798 100644
--- a/src/gb/gprs_ns2_vc_fsm.c
+++ b/src/gb/gprs_ns2_vc_fsm.c
@@ -438,6 +438,7 @@
 		break;
 	case GPRS_NS2_EV_RX_BLOCK:
 		priv->initiate_block = false;
+		priv->accept_unitdata = false;
 		ns2_tx_block_ack(priv->nsvc);
 		osmo_fsm_inst_state_chg(fi, GPRS_NS2_ST_BLOCKED,
 					0, 2);