config: Allow timeout for all sevices
    
    Allow option "timeout" for all sevices.
    Also remove unused macro CONFDB_SERVICE_TIMEOUT.
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/3068
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit 1b9b5477027d86a2afb2e72981253d108c5398da)