implement pause/unpause for VMs
add VE kill support to _stop and _set_stopped_state
handle all possible VE states in reboot method

Docstring in base driver class says, that if reboot method
is completed succesfully - it means the VM has been restarted, no
matter in which state it was before.
implement get_host_ip_addr method
add functions _create_blank_vm and _set_boot_device

Add functions which will help to implement 'boot from volume'
feature. The code is moved/copied from template.py.
add missing option num_iscsi_scan_tries

Add missing option to volume.py.
implement 'boot from volume' feature

For booting from volume we need to create a blank
VM, then attach volume to it and set it as first boot
device.