pool_acl: add test cases for storage-pool api 'read' and 'getattr'

By default, access for storage-pool api 'read' and 'getattr' is
granted for unprivileged user, add test cases for this via pool list
and dumpxml command.

Signed-off-by: Wayne Sun <gsun@redhat.com>
Merge pull request #339 from waynesun09/acl_pool_misc

pool_acl: add test cases for storage-pool api 'read' and 'getattr'