Comment 5 for bug 1602229

RCA:
1. The problem was added a long time ago on Nov 19, 2015 in the commit:
https://github.com/openstack/fuel-main/commit/2a5b896bcf2048c7c7d050a43890dbe3816c63e9#diff-271600620e265f5cd9858ad050e629ccR457
when the kickstart script was split into pieces (snippets).

2. As a result, finally we got this piece of code: https://github.com/openstack/fuel-main/blob/stable/mitaka/iso/ks.template#L443-L467
where we lost the value of the ${FS} variable.

3. Also we never have the workaround in the line: https://github.com/openstack/fuel-main/blob/stable/mitaka/iso/ks.template#L461
as we have in the line: https://github.com/openstack/fuel-main/blob/stable/mitaka/iso/ks.template#L464
which can solve the unmount issues.

4. The problem with unmount is specific to the hardware (HP iLO gen8 in this case) and its configuration, so the problem why we have never seen it before - because QA didn't test 'Installation of the Fuel master node via IPMI on certified servers'.