Unset CONFIG_FILE env var if in standalone environment

There was a bug where we were setting it to nothing rather than
unsetting it, we think it might be causing other issues.

Change-Id: I06df6e9ed9f84414a5ee8765b255574952b281e9
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/71530
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Reviewed-by: Matt Derksen <mderkse1@us.ibm.com>
Reviewed-by: William G. Hoffa <wghoffa@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/build/citest/setup-env

@@ -37,15 +37,15 @@ echo "MACHINE IS $MACHINE"
 if [ "$CHIP" == "NIMBUS" ];
 then
     export PNOR=nimbus.pnor
-    export CONFIG_FILE=
+    unset CONFIG_FILE
 elif [ "$CHIP" == "CUMULUS" ];
 then
     export PNOR=cumulus.pnor
-    export CONFIG_FILE=
+    unset CONFIG_FILE
 elif [ "$CHIP" == "CUMULUS_CDIMM" ];
 then
     export PNOR=cumulus_cdimm.pnor
-    export CONFIG_FILE=
+    unset CONFIG_FILE
 elif [ "$CHIP" == "FSPBUILD" ];
 then
     export PNOR=ZZ.pnor