Set requirement for cmd2

Workaround for https://github.com/python-cmd2/cmd2/issues/421
Change-Id: Ie887edbde9b77a91b9a3c9b0620cdabac1200873
diff --git a/tcp_tests/requirements.txt b/tcp_tests/requirements.txt
index 86ef693..64769ed 100644
--- a/tcp_tests/requirements.txt
+++ b/tcp_tests/requirements.txt
@@ -21,3 +21,4 @@
 netaddr
 mock>=1.2
 python-jenkins
+cmd2<0.9
\ No newline at end of file