Backport most important bug fixes
    
    Resolves: upstream#3523 - ABRT crash - /usr/libexec/sssd/sssd_nss in
                              setnetgrent_result_timeout
    Resolves: upstream#3562 - Use-after free if more sudo requests run and one
                              of them fails, causing a fail-over to a next server
    Resolves: upstream#3588 - sssd_nss consumes more memory until restarted
                              or machine swaps
    Resolves: failure in glibc tests
              https://sourceware.org/bugzilla/show_bug.cgi?id=22530
    Resolves: upstream#3451 - When sssd is configured with id_provider proxy and
                              auth_provider ldap, login fails if the LDAP server
                              is not allowing anonymous binds
    Resolves: upstream#3285 - SSSD needs restart after incorrect clock is
                              corrected with AD
    Resolves: upstream#3586 - Give a more detailed debug and system-log message
                              if krb5_init_context() failed
    Resolves: rhbz#1479283 - proxy to files does not work with
                             implicit_files_domain
    Resolves: rhbz#1431153 - SSSD ships a drop-in configuration snippet
                             in /etc/systemd/system