bind_receiver_resp_test.c: Fix compilation warning

/home/pespin/dev/sysmocom/bin/../git/libsmpp34/test_pdu/bind_receiver_resp_test.c: In function ‘main’:
/home/pespin/dev/sysmocom/bin/../git/libsmpp34/test_pdu/bind_receiver_resp_test.c:55:58: warning: ‘snprintf’ output
 truncated before the last format character [-Wformat-truncation=]
     snprintf((char*)b.system_id, sizeof(b.system_id), "%s", "1234567890123456");
                                                          ^
/home/pespin/dev/sysmocom/bin/../git/libsmpp34/test_pdu/bind_receiver_resp_test.c:55:5: note: ‘snprintf’ output 17
bytes into a destination of size 16
     snprintf((char*)b.system_id, sizeof(b.system_id), "%s", "1234567890123456");

Change-Id: I4ec682a5e2ee4d02008a9c86a0a5507792667d0e
diff --git a/test_pdu/bind_receiver_resp_test.c b/test_pdu/bind_receiver_resp_test.c
index 610effd..e1817e8 100644
--- a/test_pdu/bind_receiver_resp_test.c
+++ b/test_pdu/bind_receiver_resp_test.c
@@ -52,7 +52,7 @@
     b.command_id       = BIND_RECEIVER_RESP;
     b.command_status   = ESME_ROK;
     b.sequence_number  = 1;
-    snprintf((char*)b.system_id, sizeof(b.system_id), "%s", "1234567890123456");
+    snprintf((char*)b.system_id, sizeof(b.system_id), "%s", "123456789012345");
 
     tlv.tag = TLVID_sc_interface_version;
     tlv.length = sizeof(uint8_t);