Use a timeout when skipping remaining result data

When the NSS modules closes the connection and skips any remaining
result data, wait for up to 500 msec to read any available data.

See:
https://bugzilla.redhat.com/show_bug.cgi?id=1003011
In nslcd, log EPIPE only on debug level

See:
https://bugzilla.redhat.com/show_bug.cgi?id=1003011