Update requirements for oslo.config

Sometimes olf version of oslo.config(5.x.x) is installed on the env,
that leads to random errors with unpacking oslo group, opts

So set minimal version to 6.2.1

Change-Id: Ibfdc2cbf318119ce5e720c89fb6bd6f8909ca1f7
diff --git a/tcp_tests/requirements.txt b/tcp_tests/requirements.txt
index 3d1b4d2..ca2d0a1 100644
--- a/tcp_tests/requirements.txt
+++ b/tcp_tests/requirements.txt
@@ -5,7 +5,7 @@
 paramiko
 six
 requests>=2.2.0
-oslo.config>=3.12.0 # Apache-2.0
+oslo.config>=6.2.1 # Apache-2.0
 pytest>=2.9,<=3.2.5
 docker-py
 docker-compose==1.7.1