rh stateless support. remove the tmp and root dir mount requirement in fstab. They can be handled correctly by dracut and dracut cfg file

xCAT-server/share/xcat/netboot/rh/compute.rhels7.x86_64.postinstall

@@ -25,9 +25,6 @@ cat <<END >$installroot/etc/fstab
 proc            /proc    proc   rw 0 0
 sysfs           /sys     sysfs  rw 0 0
 devpts          /dev/pts devpts rw,gid=5,mode=620 0 0
-${profile}_${arch}      /        tmpfs  rw 0 1
-none            /tmp     tmpfs  defaults,size=10m 0 2
-none            /var/tmp tmpfs  defaults,size=10m 0 2
 END
 
 #-- Uncomment the line contains "cons" in /etc/inittab