Added an option to disable known_hosts autopopulation

Prod-Related: PROD-34958
Change-Id: Idb8e79f3442b730bab0ea17614f9563cf539174a
diff --git a/tests/test-requirements.txt b/tests/test-requirements.txt
index 7188b2b..bc7dc7f 100644
--- a/tests/test-requirements.txt
+++ b/tests/test-requirements.txt
@@ -1,3 +1,4 @@
 jsonschema
 reno
 setuptools<45.0.0
+msgpack<1.0.0