VMware: spawn refactor - DatastorePath class

Part of spawn refactor work to consolidate a lot of the datastore path
manipulation code. The DatastorePath class is a simpler version of a
class of the same name in earlier versions of
https://review.openstack.org/#/c/87002, and is intentionally limited in
the ways that DatastorePath objects can be constructed. No attempts are
made to ensure that the datastore, directories and files referenced in
these objects are valid on the remote system.

partial blueprint vmware-spawn-refactor

Change-Id: Id65d0308d32835048229e7a3d98b84af2b13583c
VMware: remove dsutil.split_datastore_path

The functionality of split_datatore_path has been subsumed by
the DatastorePath utility class, so remove it and convert
all callers to use the latter.

Change-Id: I07a2cfe15fccaca4aee25bc43157e6c604b91831
VMware: spawn refactor - Datastore class

Introduces the start of a simple Datastore class to encapsulate relevant
data of a datastore.

partial blueprint vmware-spawn-refactor

Change-Id: Ic0ee6cdd47e7cbd66cf456776c61d0b85fb51a0a
Use _set_instance_obj_error_state in compute manager set_admin_password

The set_admin_password operation is not a lifecycle operation like
building or deleting an instance, or resize for that matter, so replace
usage of _set_instance_error_state which does a host stats update with
_set_instance_obj_error_state which just sets the instance state to
error and handles any InstanceNotFound exception (in case we still want
to be a little paranoid).

Part of blueprint compute-manager-objects-juno

Change-Id: Ie1d1075095ed5d318d0d7a638526bc5cd40d4583
Use ebtables to isolate dhcp traffic

Iptables doesn't properly block the broadcast traffic crossing
the bridge, so use ebtables instead. Removes test which is no
longer valid since we are not using iptables anymore.

Change-Id: I43e5f1fe9512dd3ec9595c7203bc46837cef3cad
Closes-Bug: #1318104
Merge "Use _set_instance_obj_error_state in compute manager set_admin_password"
Merge "Use ebtables to isolate dhcp traffic"
Merge "VMware: spawn refactor - DatastorePath class"
Merge "VMware: remove dsutil.split_datastore_path"
Merge "VMware: spawn refactor - Datastore class"