move nova v3 delete image tests into glance testing

There is no image api in nova v3 api. so move the tests
that just test glance into glance testing from nova v3
testing. The rest tests in compute.v3.image.test_images
just are the tests related to nova, like creating image
from a server. Also move the negative tests in test_image
to a separate file.

Partially implements blueprint nova-v3-api-tests

Change-Id: I42c0f08434de4a51d41f2fafd95cfaf72a9dd6da
Remove unused run_ssh variable

'run_ssh' of class variable is not used. This commit removes it.

Change-Id: I06d275d74192326bae09bd294013124c3771b08f
Merge "move nova v3 delete image tests into glance testing"
Merge "Remove unused run_ssh variable"