Fixed missing -o option in command

Change-Id: Ia605f85d305a254e97f56d566ec712188da2e043
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/security/test_bmc_ssh_security.robot b/security/test_bmc_ssh_security.robot
index 7ea06fe..88accd0 100644
--- a/security/test_bmc_ssh_security.robot
+++ b/security/test_bmc_ssh_security.robot
@@ -49,7 +49,7 @@
     # - KEX: diffie-hellman-group1(any) , (any) SHA1
 
     Printn
-    ${ssh_cmd_buf}=  Catenate  ssh -o NumberOfPasswordPrompts=0 UserKnownHostsFile=/dev/null
+    ${ssh_cmd_buf}=  Catenate  ssh -o NumberOfPasswordPrompts=0 -o UserKnownHostsFile=/dev/null
     ...  -o StrictHostKeyChecking=no -vv ${OPENBMC_HOST} 2>&1
 
     ${rc}  ${std_err}=  Shell Cmd  ! ${ssh_cmd_buf}