test-rebuild.sh: test if package is installed before yum install

test-rebuild.sh

@@ -32,7 +32,7 @@ mkdir -p $TMP/
 PKGS=$(cd $ARCH; rpm -qp $(ls *-$VERREL*.rpm))
 
 for i in $PKGS; do
-  sudo yum install -q $i
+  rpm -q --quiet $i || sudo yum install -q $i
   for k in list requires provides scripts; do
     rpm -qp --$k $ARCH/$i.rpm | grep -v rpmlib > $TMP/$i.$k.test
     rpm -q --$k $i | grep -v rpmlib > $TMP/$i.$k.installed