Pass ${installdrive} and ${forceformat} to kickstart

Enable possibility to pass this variables allows user
to automate installation of fuel-master with customization only
grub cmdline.

Closes-bug: #1535712
Change-Id: Ib07f4717aea1f5316d675178ee125c50d8e2c69a

iso/ks.template

@@ -90,8 +90,8 @@ for drv in `ls -1 /sys/block | grep "sd\|hd\|vd\|cciss"`; do
 done
 default_drive=`echo ${drives} ${removable_drives} | awk '{print $1}'`
 
-installdrive="undefined"
-forceformat="no"
+installdrive=${installdrive:-undefined}
+forceformat=${forceformat:-no}
 for I in $(cat /proc/cmdline); do
   case "$I" in
     *=*)