tests: UnixStreamTransport test suite improvements

refs #3305

Change-Id: I6c6ca52a5e80266920ded811ff45fc568c3e59b9
diff --git a/tests/daemon/face/get-available-interface-ip.hpp b/tests/daemon/face/get-available-interface-ip.hpp
index feadabe..3a98632 100644
--- a/tests/daemon/face/get-available-interface-ip.hpp
+++ b/tests/daemon/face/get-available-interface-ip.hpp
@@ -50,7 +50,7 @@
 getAvailableInterfaceIp();
 
 template<>
-boost::asio::ip::address_v4
+inline boost::asio::ip::address_v4
 getAvailableInterfaceIp()
 {
   for (const auto& interface : listNetworkInterfaces()) {
@@ -68,7 +68,7 @@
 }
 
 template<>
-boost::asio::ip::address_v6
+inline boost::asio::ip::address_v6
 getAvailableInterfaceIp()
 {
   for (const auto& interface : listNetworkInterfaces()) {