cache_req: add object by id
This request returns either user or group object.
Resolves:
https://fedorahosted.org/sssd/ticket/3151
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
(cherry picked from commit 3be2628d8aba6aeb99ac1484da990f1fad8169ec)
Only sysdb changes were cherry picked from previous commit
(cherry picked from commit f84055ee1c4ad60219e5d9b2ea5cc4dd6e1112eb)