Add missing HTTPS_PORT reference

Without this reference all tests in this section fail
on non-standard ports.

Change-Id: I90db7c345d35f328d875fe4fad1791c563f73600
Signed-off-by: Matt Fischer <matthew.fischer@hpe.com>
diff --git a/redfish/service_root/test_service_root.robot b/redfish/service_root/test_service_root.robot
index 0c7212f..9e4c2ba 100644
--- a/redfish/service_root/test_service_root.robot
+++ b/redfish/service_root/test_service_root.robot
@@ -106,7 +106,7 @@
     [Documentation]  Login to BMC via redfish session service.
     [Tags]   Redfish_Login_Via_SessionService
 
-    Create Session  openbmc  https://${OPENBMC_HOST}
+    Create Session  openbmc  https://${OPENBMC_HOST}:${HTTPS_PORT}
     ${headers}=  Create Dictionary  Content-Type=application/json
     ${data}=  Set Variable  {"UserName":"${OPENBMC_USERNAME}", "Password":"${OPENBMC_PASSWORD}"}