Rename policy auth for V3 os-fixed-ips

Renames name used to for policy authorisation for the
V3 os-fixed-ips to os-fixed-ips with a "v3:" prefix (as
per ML discussion)

Change-Id: Ia599c29d7f45153ef47605b6e2a7061fc28ff7cc
Don't delete sys_meta on instance delete

Unfortunately, we require to access instance_system_metadata to get
data (specifically at least instance_type data) for instances that have
been deleted.

There's 2 cases where this is true:

1) nova-api supports showing deleting instances when you specify a
'changes-since' param.
2) The _usage_audit_log periodic task pulls all instances during the
audit period, which includes instances that have been deleted during
that period.

This reverts commit 17bca438954638d74035d560e826a26a532b3ea3, which was
attempting to fix a bug where we leave instance_system_metadata entries
undeleted from the DB.  There's not an easy way to query for the deleted
sys_meta data in an efficient manner, and leaving the entries undeleted is
the lesser of the 2 evils for now.

Fixes bug 1185190

Change-Id: I898f0546c49126dcc56a4237120082f95dc82304
Merge "Don't delete sys_meta on instance delete"
Merge "Rename policy auth for V3 os-fixed-ips"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp