Establish SSH connection before performance check

There was a failure due to "SSHException: SSH session not active".
This turns out to be due to BMC reaching to standby longer than
expected and the previous SSH conncetion taken during version
verification expires.

The right thing to do before any Execute Command is to take the
session and execute.

Change-Id: I32f3c37e3eef44c37718166f6b8c8fa4db2e12ec
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/extended/code_update/update_bmc.robot b/extended/code_update/update_bmc.robot
index 89ff819..664bdbf 100644
--- a/extended/code_update/update_bmc.robot
+++ b/extended/code_update/update_bmc.robot
@@ -79,5 +79,7 @@
     ...    10 min   10 sec   Verify BMC State   BMC_READY
 
 Test BMC CPU Mem Performance at Ready State
+    [Documentation]   Check performance of memory and BMC CPU.
+    Open Connection And Log In
     Check BMC CPU Performance
     Check BMC Mem Performance