tweek Xvfb handling

releng.control/cc.sh

@@ -11,6 +11,10 @@ then
    source ${RELENG_CONTROL}/commonComputedVariables.shsource
 fi
 
+if [ -z $DISPLAYNUMBER ]
+then
+DISPLAYNUMBER=1001
+fi
 
 # limit data space (ld) to 10m bytes. 
 # limit stack space (ls) to 1m bytes.