Default to system CA bundle if no CA certificate is provided

If no CA certificate is provided to be used for validation then
fall back to the system-wide CA bundle as presented by
python-requests.

Change-Id: I05206a868150d4b62b6f1b833310eb9b86b7c4f8
Closes-bug: #1362179
Stop using intersphinx

Remove intersphinx from the docs build as it triggers network calls that
occasionally fail, and we don't really use intersphinx (links other
sphinx documents out on the internet)

This also removes the requirement for internet access during docs build.

This can cause docs jobs to fail if the project errors out on
warnings.

Change-Id: I71e941e2a639641a662a163c682eb86d51de42fb
Related-Bug: #1368910
Adds support for Glance Tasks calls

Add tasks operations on client side to support task create,
list all and show.

DocImpact
Implement blueprint async-glance-workers

Change-Id: Ib4b8e347a8a47817e3b427c8ba024e8c32f65155
Skip non-base properties in patch method

It's currently impossible to update properties which are defined in
image schema and which are not a base image property. Proposed fix skips
every non-base property when building a json patch, that is used to
update image properties through glance API.

Change-Id: I3b35cef379fcf437715e2966f9a0d25c1b4e4016
Closes-Bug: #1371559
Merge "Skip non-base properties in patch method"
Remove network_utils

Use oslo.utils instead

Change-Id: I4830b13794db5570e7dde4a897a7396065028e37
Merge "Default to system CA bundle if no CA certificate is provided"
Merge "Remove network_utils"
Merge "Stop using intersphinx"
Merge "Adds support for Glance Tasks calls"