Adds more policy control to cells ext

Allow create,delete,update and sync_instances to
have fine grained policy control.

UpgradeImpact
DocImpact

Change-Id: I2e32ae2f37d3b599585d25535c79eecf6485b462
Closes-Bug: 1335901
Fix nova cells exiting on db failure at launch

We have seen cases where db errors at launch can cause cell
services to exit without retrying.  The service shouldn't
exit __init__ much like it doesn't later by handling
this type of exceptions.  We'll wait an hour and
then give up.

Change-Id: I24c9eb811d50d1fa6a5e4a5f595ebf68ded3b7b5
Closes-Bug: 1342257
VMware: do not cache image when root_gb is 0

Save space on datastore when the instance size has root_gb of
0. There is no need to cache the disk as it already exists on
the datastore.

TrivialFix

Change-Id: Iac75d97f40a1a91b8fa2df7fb4318fc2965fd93a
Closes-bug: #1304593
Convert to importutils

We had some remaining users of __import__ that really deserved to
be converted to oslo's importutils.

Change-Id: I8c0c3e885151018b974025087a4abc96dd6ae77c
Add quota limit create/update methods to Quotas object

This adds two methods to the Quotas object that are effectively
passthroughs to the DB api calls. Since the Quotas object isn't
actually a representation of what is in the database, and because
we've (incorrectly) got some logic in the DB API around how the
quotas are applied, this is just a temporary step. Ideally, we
would (will) refactor Quotas in several ways in the near future,
at which time the way all of this works can be revisited and
cleaned up.

Related to blueprint compute-manager-objects-juno

Change-Id: If93614cd27e56667e0f106e8045dd1adc633ff1b
Merge "Convert to importutils"
Merge "Adds more policy control to cells ext"
Merge "VMware: do not cache image when root_gb is 0"
Fix and Gate on E265

pep8 E265 makes sure block comment start with '# '. Fix and gate on this
new rule as it helps improve comment readability.

In the few cases where the comment was just commented out code, remove
the comment.

Change-Id: Iea1c445df8ddc2b6c17a4ab697ad756eef2f91fa
Merge "Add quota limit create/update methods to Quotas object"
Merge "Fix nova cells exiting on db failure at launch"
Merge "Fix and Gate on E265"