Improve product install task

Map all install tasks and use the task reference instead of leaving for
fabric selecting them. Using directly the reference is better when
automation_tools is used as a library.
Merge pull request #82 from elyezer/improve-product-install

Improve product install task
Improve vm_destroy task

Now vm_destroy uses virsh to remove the volume image because it removes
the image file and refreshes the volumes pool.
Merge pull request #83 from elyezer/improve-vm-destroy

Improve vm_destroy task