Always set ISTEP_MODE based on scratch reg

  - Currently ISTEP_MODE was only ever getting set, which would
    result in it being permanently stuck in istep mode after a
    successful boot.  Change to clear/set based on scratch reg
    flag

Change-Id: I0d6061502ee7454c7f3d2356b1f127bc810636be
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/36891
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Reviewed-by: Prachi Gupta <pragupta@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/usr/targeting/targetservicestart.C

@@ -313,6 +313,10 @@ static void initializeAttributes(TargetService& i_targetService,
             {
                 l_pTopLevel->setAttr<ATTR_ISTEP_MODE>(1);
             }
+            else
+            {
+                l_pTopLevel->setAttr<ATTR_ISTEP_MODE>(0);
+            }
 
             //Set the RISK_LEVEL ATTR based off of master Scratch regs
             INITSERVICE::SPLESS::MboxScratch5_t l_scratch5;