Respond to AdminCheckRequest with AdminCheckResponse

Respond to AdminCheckRequest with AdminCheckResponse

Change implementation of both service and admin library Logic layers
so they use AdminCheckResponse instead of CheckResponse as a reply
for AdminCheckRequest.

This change allows passing additional information about existence
or vacancy of start bucket given in AdminCheckRequest.
In case of vacancy of such bucket in cynara database cynara-admin
library returns CYNARA_API_BUCKET_NOT_FOUND from cynara_admin_check()
function.

This fixes also a bug that was hidden in service Logic. Passing
unexisting bucket causes cynara service to stop because of an unhandled
exception.

Change-Id: Ibf65a69c35ba92ea62bee91a67f43975b97052ca