SoL tests: skip power operations when they aren't needed

Skip 'Redfish Hard Power Off' command if a system is
already in the powered off state.

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
Change-Id: Ic468f66e3bb44e7239b8e87c5295fc3f40bdd69c
diff --git a/ipmi/test_ipmi_sol.robot b/ipmi/test_ipmi_sol.robot
index 941d4dd..199063b 100644
--- a/ipmi/test_ipmi_sol.robot
+++ b/ipmi/test_ipmi_sol.robot
@@ -127,7 +127,7 @@
     [Documentation]  Verify SOL during boot.
     [Tags]  Verify_SOL_During_Boot
 
-    Redfish Hard Power Off
+    Redfish Hard Power Off  stack_mode=skip
     Activate SOL Via IPMI
     Initiate Host Boot Via External IPMI  wait=${0}
 
@@ -249,7 +249,7 @@
 
     Should Be Equal  '${setting_value}'  '${expected_value}'
 
-    Redfish Hard Power Off
+    Redfish Hard Power Off  stack_mode=skip
 
     Initiate Host Boot Via External IPMI  wait=${0}