although python-openstackclient run command(image import) with invalid uri,
but the request succeeds. Fixed it to throw an exception
when requesting with an invalid URI.
unit test added. the test cover --uri 'invalid value'
Task: 52251
Story: 2011468
Closes-Bug: 2111777
Change-Id: I62cd8cdf054b6a5e07d664a543b0923ce5f20f83
9ad18c4967