tests/net/gnrc_sixlowpan_frag_sfr_congure_impl: increase send interval

socket ZEP now tries to simulate airtime.

tests/net/gnrc_sixlowpan_frag_sfr_congure_impl/tests/01-run.py

@@ -127,7 +127,7 @@ def test_fragmentation(factory, zep_dispatch):
         # 2 intermediate hops, 64 - 2
         assert_result(result, 34, 1, 64 - 2)
 
-        result = parser.parse(D.ping6(root_addr, count=100, interval=30, packet_size=500))
+        result = parser.parse(D.ping6(root_addr, count=100, interval=200, packet_size=500))
         # assert packetloss is under 90%
         # assert at least one response
         # 2 intermediate hops, 64 - 2