Glance image list API supports pagination, but `_get_service_image`
uses novaclient.glance.list() that only return images in one page.
When the image needed by share server is not returned in the first
page, the exception occurs. This patch uses `find_image` method
to get the image.
Since latest novaclient has no proxy to lookup image, so only
novaclient.glance.
Change-Id: I57b15b7ebb29c545c9780a90734988565fa1f6b7
Closes-Bug: #1844046
