Use client error codes in admin libraries

Use client error codes in admin libraries

We need to have one unified set of error codes. Client
error codes have been adjusted to serve admin errors
too. Then client error codes were used in admin
libraries keeping following mapping:
CYNARA_ADMIN_API_SUCCESS
   -> CYNARA_API_SUCCESS
CYNARA_ADMIN_API_OUT_OF_MEMORY
   -> CYNARA_API_OUT_OF_MEMORY
CYNARA_ADMIN_API_INVALID_PARAM
   -> CYNARA_API_INVALID_PARAM
CYNARA_ADMIN_API_SERVICE_NOT_AVAILABLE
   -> CYNARA_API_SERVICE_NOT_AVAILABLE
CYNARA_ADMIN_API_UNEXPECTED_CLIENT_ERROR
   -> CYNARA_API_UNKNOWN_ERROR
CYNARA_ADMIN_API_OPERATION_NOT_ALLOWED
   -> CYNARA_API_OPERATION_NOT_ALLOWED
CYNARA_ADMIN_API_BUCKET_NOT_FOUND
   -> CYNARA_API_BUCKET_NOT_FOUND

Remove not needed anymore old admin error codes file:
src/include/cynara-admin-error.h

Change-Id: Ice8990a2b354bd489c67c2a004344a5c60fc15ee