Send `identity_headers` through the wire

Change I09f70eee3e2777f52ce040296015d41649c2586a, introduced a bug where
the identity_headers are not added to the request headers anymore
causing the former to be completely ignored and useless.

This patch fixes that issue by restoring the previous code. A new test
has been added to avoid regressions.

Closes-bug: #1394965
Change-Id: I1b1633636448398cf3f41217f1d671b43ebd9946
Allow --file in image-create with v2 Image API

Allows passing --file and --progress to glance image-create with Image API v2.

if --file is present the image-create effectively calls image-upload with the
newly created image's id and the '--file' + '--progress' paramaters. The image
metadata will be printed after the upload call instead of after creation.

In a case argumented file does not exist the image will not be created and
error will be printed instead.

DocImpact
Closes-Bug: #1324067

Change-Id: I5d41fb2bbeb4e56213ae8696b84bf96b749414f8
Merge "Allow --file in image-create with v2 Image API"
Merge "Send `identity_headers` through the wire"