VMware: delete vm snapshot after nova snapshot

When performing a nova snapshot, the vmware driver takes a VM snapshot
and copies out the snapshotted disk. After the operation, the VM
snapshot should be deleted, to prevent growing disk chain(s) on each nova
snapshot.

Closes-Bug: #1252967
Change-Id: I7861ccce0153e45eea0316a2e8dd824210db1660
VMware: enable booting an ISO with root disk size 0

There may be cases where booting from an ISO does not require
any local disk. In this case the flavor may have the root disk
size set at 0.

Change-Id: Id290a0ede11c754f686d3b70322c84c03f161637
Closes-bug: #1292633
Fix comment for block_migration in nova/virt/libvirt/driver.py

Change-Id: Iab2896189f70420e1e15779e6632cb3a33e1c321
Closes-bug: 1293353
Increase volume creation max waiting time

In some cases waiting 60sec, is not enough for cinder volume to be created.
For example, a 20Go LVM volume (hosting a Windows Image) would take 100sec
to be copied assuming a 200Mo/s cinder volume backend.

Issue has already been discussed in I6bcd395a where a config option was
rejected.

This patches raises the max timeout at 180sec.

Change-Id: I7e739fc20af0ae963269459b5e224c4a8b7bb87d
Partial-Bug: #1253612
Partial-Bug: #1272076
Added missing raise statement when checking the config driver format

Closes-bug: #1275772

Change-Id: I636525d0272511d4192c43d18c56e867fb7514d8
Merge "Added missing raise statement when checking the config driver format"
Merge "VMware: delete vm snapshot after nova snapshot"
Merge "VMware: enable booting an ISO with root disk size 0"
Merge "Increase volume creation max waiting time"
Merge "Fix comment for block_migration in nova/virt/libvirt/driver.py"