add checksums to udp independent of /dev/vhost-net.

In newer kernel versions, the network devices added for lxc containers
do not get checksums added.  The result is the same as previously
occurred when vhost-net became prevalent in kvm guests.

Software that expects the checksums on packets will ignore them.  One example
of such software is udhcpc in cirros.  Without this change, cirros containers
in 3.13 kernels (Ubuntu 14.04) will fail to acquire an address via dhcp.

Closes-Bug: #1335193
Change-Id: Iba305fb7f8236955ca732e467db9e424535be93d
Correct exception for flavor extra spec create/update

When create/update flavor extra spec failed for v2 api, it will not
raise MetadataLimitExceeded for but two exceptions as following:
1) FlavorExtraSpecUpdateCreateFailed
2) FlavorNotFound

When create/update flavor extra spec failed for v3 api, it will not
raise DBDuplicateEntry but raise FlavorExtraSpecUpdateCreateFailed.

This patch updates the exception handling logic for create/update
flavor extra spec.

Change-Id: If3310a1cb44952e8fe2efe0b3358783f729bc190
Small grammar fix in libvirt/driver.py. fix all occurrences.

Change wording to be more descriptive/correct for greenthread.sleep()
Change-Id: I074391eaa7cfd580b89d89c2dd587796112c4a98
shelve doesn't work on nova-cells environment

The compute_api shelve/unshelve methods expect an Instance object,
but cell is still passing the sqlalchemy form.
So adding shelve/unshelve to the list of methods that will receive an
Instance object when using nova-cell.

When shelving instance with nova-cell environment,
instance object needs to contain 'metadata' and 'info_cache'.
So fetching the same from databse and adding it to
instance object before calling shelve/unshelve methods.

Closes-Bug: #1338451
Change-Id: Ia31b33c9a1d347f15d3e0a67fa31ef6b25a7407a
Merge "add checksums to udp independent of /dev/vhost-net."
Merge "shelve doesn't work on nova-cells environment"
Merge "Small grammar fix in libvirt/driver.py. fix all occurrences."
Merge "Correct exception for flavor extra spec create/update"