deploy: Fix: remove storage files explicitly

deploy: Fix: remove storage files explicitly

Previous change [1] tried to move the responsibility of removing
storage files (raw, iso) from our python scripts to libvirt.

Although this works as expected for non-root invocations, like
Armband deploys, it fails to remove raw files in Fuel@OPNFV deploys.

Work around this by keeping both mechanisms (libvirt managed +
python explicit handling).

Related-bug: ARMBAND-128

[1] https://gerrit.opnfv.org/gerrit/#/c/22447

Change-Id: Ib846cd6071705b71d98824385835d724c729fd78
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>