fix N401 errors, stop ignoring all N4* errors

We had previously been ignoring all our custom N4xx hacking.py
errors. This fixes all the N401 errors "doc strings
should not start with a space" and reduces the ignore set down
to N402 only "single line docstrings should end with period".

It also fixes the N401 parser to catch only docstrings, and
not tripple quoted string blocks used later on in a function.

Clean up a few of the more crazy uses of """ in our code

Clean up additional funky comments to make indents a bit more
consistent, and pull in lines when possible.

Change-Id: I9040a1d2ca7efda83bd5e425b95d1408b5b63577
Move global glance opts into nova.image.glance

Move the glance_host, glance_port and glance_protocol options into the
nova.image.glance module.

Also move the generate_glance_url() and generate_image_url() utility
methods there since they're the only uses of the options outside of the
module.

blueprint: scope-config-opts
Change-Id: I3beca1a65cdd902a94ddc1c512d79a4de635ef38
Fix serialization in impl_zmq.

Sync rpc from oslo-incubator to include some fixes to impl_zmq:

    https://review.openstack.org/#/c/18913/

Change-Id: I5f5c157e81026c108df04bd385776a9985d4a497
add to driver option to keep disks when instance destroyed

Adding delete_disks flag to destroy instance method.
In case it's false the driver keeps disks.
*required for blueprint rebuild-for-ha

DocImpact

Change-Id: I38c7833114d8414dff831c9cc0c04c4610dbd33a
Co-authored-by: Oshrit Feder <oshritf@il.ibm.com>
Add to libvirt driver instance_on_disk method

Added method to driver layer to validate that instance directory
accessible from the host.

part of libvirt driver support for blueprint rebuild-for-ha

DocImpact

Change-Id: I9c6a3aec99f61bd4fb6bc4b4264771e077aae96a
Co-authored-by: Oshrit Feder <oshritf@il.ibm.com>
Adds to manager init_host validation for instances location

While the compute was down the instances running on it could be
evacuated to another host. The method checks that instance host
identical to current host. Otherwise destroying it.

part of blueprint rebuild-for-ha

DocImpact

Change-Id: Ic90df2b2887ee203e6d8261084e3f97773c5d81c
Co-authored-by: Oshrit Feder <oshritf@il.ibm.com>
Clarify the DBApi object in cells fakes

Adds a docstring and makes instance_get_by_uuid() raise by default.
It's only used as a stubbing point, but returning 'None' is not really
valid and having it raise might save someone some confusion in the
future.

Change-Id: Ie3fa333288f9c0263ead69c2d307101b8583dea7
Merge "fix N401 errors, stop ignoring all N4* errors"
Merge "Fix serialization in impl_zmq."
Merge "add to driver option to keep disks when instance destroyed"
Merge "Add to libvirt driver instance_on_disk method"
Merge "Clarify the DBApi object in cells fakes"
Merge "Adds to manager init_host validation for instances location"
Merge "Move global glance opts into nova.image.glance"