Adds the bookie cookie query service for http api

[SongOf]

Descriptions of the changes in this PR:

Motivation

When bookie A is decommissioned, the user cannot know whether the decommissioning process is complete. Considering that bookie cookies are deleted after decommissioning, the user can determine whether decommissioning is complete by checking if bookie A's cookies still exist.

The shell admin provides a GetCookieCommand to query cookies for a specified bookie_id, and the HTTP admin also needs to provide an API to query cookies for a specified bookie_id.

Changes Adds an API to get the cookie of bookie at /api/v1/bookie/cookie.