Add test for secret-define/undefine
secret_define_undefine: Add libvirt API acl test case for secret commands

Update secret_define_undefine case for cover virStoragePoolPtr set
acl testing. The covered APIs in the case are 'delete', 'save',
'read-secure', and 'write'.

Signed-off-by: Wayne Sun <gsun@redhat.com>
Merge pull request #115 from kylazhang/secret-define-undefine

Add test for secret-define/undefine