[cloudstack] add delete_snapshot request mock, fix delete_snapshot description comments
[cloudstack] add list_snapshots request mock
[cloudstack] add test volume to mock data
[cloudstack] tests, add snapshots_attributes to cloudstack provider config
[cloudstack] tests, fix snapshot test
[cloudstack] tests, remove unreachable code in snapshot test, add testcase for volume relation
Merge pull request #1768 from dm1try/cloudstack_fix_snapshot_tests

[cloudstack] fix snapshot tests