As of Nova API microversion 2.47, response of GET /servers/detail has flavor
which contains a subset of the actual flavor information used to create the
server instance, represented as a nested dictionary.
Since current watcher nova default api version is 2.53(Pike), This patch
follows the API response change.
Change-Id: Ia575950f0702afa1d093f03ca8ddedd3c410b7de
Closes-Bug: #1722462