s3: lib: libsmbclient: If reusing a server struct, check every cli->timout milisecond...

s3: lib: libsmbclient: If reusing a server struct, check every cli->timout miliseconds if it's still valid before use.

Uses an cli_echo() call to do so.

Based on code from <shargagan@novell.com>

Bug 11079 - libsmbclient not checking the cached connection alive status before re-using it from connection cache

https://bugzilla.samba.org/show_bug.cgi?id=11079

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>
Autobuild-User(master): David Disseldorp <ddiss@samba.org>
Autobuild-Date(master): Fri Mar 20 13:48:26 CET 2015 on sn-devel-104

(cherry picked from commit 4f4151ea050a5f34e42d73a4bf9448c673a35787)