There is a bug in systemd-209 source code: it returns
ENOENT when no more entries in a password database left.

Later the issue been fixed but we still meet the systems
where it hits. The problem affects getpwent/getgrent calls
only thus we can expect them to return the buggy error code
to skip.

Notes:

1) See systemd's commit where issue been fixed

   | commit 06202b9e659e5cc72aeecc5200155b7c012fccbc
   | Author: Yu Watanabe <watanabe.yu+github@gmail.com>
   | Date:   Sun Jul 15 23:00:00 2018 +0900
   |
   |     nss: do not modify errno when NSS_STATUS_NOTFOUND or NSS_STATUS_SUCCESS

2) Another option is to call getpwall on Tarantool startup
   unconditionally where we could simply ignore any errors. This
   is a very bad choise since traversig a password database might
   introduce significant lags if backend does some network activiy
   or have expired caches. Thus drop getpwall() unconditional call
   run it iif a user does an explicit request.

Fixes #5034

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>