Quote arguments for kickstart.file.contains and

kickstart.stream.contains

Even when quoting like `kickstart.stream.contains 'debian 5.0'` it would
not work properly.

It will now.

kickstart/recipes/kickstart/file.sh

@@ -4,5 +4,5 @@ kickstart.file.link() {
 }
 
 kickstart.file.contains() {
-  grep -q $2 $1 2>/dev/null
+  grep -q "$2" $1 2>/dev/null
 }

kickstart/recipes/kickstart/stream.sh

@@ -1,3 +1,3 @@
 kickstart.stream.contains() {
-  grep -q $1 2>/dev/null
+  grep -q "$1" 2>/dev/null
 }