gnrc_tcp: fix test part 2

tests/gnrc_tcp/tests/05-garbage-pkts.py

@@ -97,17 +97,16 @@ def test_short_header(child, src_if, src_ll, dst_if, dst_l2, dst_ll, dst_port):
 @testfunc
 def test_send_ack_instead_of_syn(child, src_if, src_ll,
                                  dst_if, dst_l2, dst_ll, dst_port):
-    # check if entering _event_loop in `@testfunc` decorator generates debug
-    # output
-    debug = child.expect([pexpect.TIMEOUT, 'GNRC_TCP'], timeout=1)
-    # with debug output the node can be overwhelmed by packets + output
+    # check if any debug output is generated during `@testfunc` decorator 
+    # execution. If so, send fewer packets to prevent the target node
+    # from being overwhelmed by packets and output.
+    debug = child.expect([pexpect.TIMEOUT,
+                          r'GNRC_TCP: Enter "\S+", File: .+(\d+)\s'], timeout=1)
     if debug:
         count = 10
     else:
         count = 1000
 
-    print(debug)
-    print(count)
     # see https://github.com/RIOT-OS/RIOT/pull/12001
     provided_data = base64.b64decode("rwsQf2pekYLaU+exUBBwgPDKAAA=")
     tcp_hdr = TCP(provided_data)