Move admin "delete a server" tests to test_servers

"delete a server" tests, which need the admin privilege, exist in
admin's test_servers. Now we have test_delete_server for testing
"delete a server", and it is better to move them into test_delete
_server for knowing the test coverage.

This patch moves admin "delete a server" tests to test_delete_server.

Change-Id: I079541df10ba7869eb5c6793e051cf93993f3972
4 files changed