Major refactor of find vm.

Previously our way of calculating the A name of a machine was:
0) ssh into dom0
1) get the vm's mac
2) grep a deprecated dhcp config on dom0 to convert the mac into an ip
address
3) shell out to dig (whilst still in dom0) to convert the ip address to
an A name.

This fails for vms that are in the DMZ, and puppies$(x) where $(x) > 31

With this patch we
0) ssh into dom0
1) get the vm's ip address
2) use the python socket module to convert that ip address into an A name.
Add a third disk for swap.

At the moment we don't have a swap disk, which means that ballooning
breaks things when the vm should be writing out to swap.

The best way of providing swap is through an extra disk. If we use
partitions, resizing is annoying as we have to move around
partitions. With a third disk, we can just delete it and add a new one.
Add a third disk for swap.

At the moment we don't have a swap disk, which means that ballooning
breaks things when the vm should be writing out to swap.

The best way of providing swap is through an extra disk. If we use
partitions, resizing is annoying as we have to move around
partitions. With a third disk, we can just delete it and add a new one.
Tidy up imports.

Removed unused imports, and remove import *
Constants in uppercase
Remove unused constant
s/validIP/valid_ip
No semantic change. Minor cleanup of syntax
One import statement per line
No semantic change. Removed whitespace around = signs for allignment as
per E221.
Two blank lines between top level fns
Prefer is None to == None
Remove excessive whitespace
Fix bug introduced in 2d7c0c where dhcp addresses were fetched from dom0 rather than dhcp
Merge branch 'swap_disk' of /srv/git/repositories/infrastructure/husky-scripts into upstream
Merge branch 'python-cleanup' of /srv/git/repositories/infrastructure/husky-scripts into upstream
Build  a VM if mac is not NULL.

Fixes bug entered in c5c04887 caused by wrong indentation
Merge branch 'python-cleanup' of /srv/git/repositories/infrastructure/husky-scripts into upstream
Add error checking that was removed in  7dda3ffc
Added a --force flag which will delete a VM even if the deleteable-by info is missing or would prevent it