TESTS: Add a module to call nss_sss's getgr* from tests
    
    Implements a python module that allows to load the nss_sss module and
    call functions that act like getgr*
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit 3728db53ac32da51fcaae96b132e8e56ebbaebfa)