TT#11444 Mount 'data' partition inside chroot

We perform all packages installation on 'root' partition.
Some packages, like faxserver for now, want to create
something on 'data' partition. They do it successfully in
Debian maintainer files (like postinst), so the 'data'
partition has to be mounted properly, otherwise the data
will be gone on reboot.

Also we need to unmount it properly at the end of installation.

P.S. we need to call mount under grml-chroot as chroot fails:
> (netscript.grml:1353): main():  chroot /mnt mount /ngcp-data
> mount: /ngcp-data: mount failed: Unknown error -1

Change-Id: Ief90d380d71ea6e0a64eba45f403465989865952

templates/scripts/includes/deployment.sh

@@ -1347,6 +1347,10 @@ if [ -n "${DATA_PARTITION}" ] ; then
   cat >> "${TARGET}/etc/fstab" << EOF
 ${DATA_PARTITION} /ngcp-data               auto           noatime               0  0
 EOF
+
+  # Make sure /ngcp-data is mounted inside chroot
+  # (some package might need to create folders structure on .postinst)
+  grml-chroot "${TARGET}" mount /ngcp-data
 fi
 
 # provide useable /ngcp-fallback read-only partition
@@ -2079,6 +2083,11 @@ if [[ "${SWRAID}" = "true" ]] ; then
   grml-chroot "$TARGET" update-grub
 fi
 
+# unmount /ngcp-data partition inside chroot (if available)
+if [ -n "${DATA_PARTITION}" ] ; then
+  grml-chroot "${TARGET}" umount /ngcp-data
+fi
+
 # don't leave any mountpoints
 sync