s4-lib/tls: Try socket_send() multiple times to send partial packets

s4-lib/tls: Try socket_send() multiple times to send partial packets

This works around an artificial limitation in socket_wrapper that breaks
some versions of GnuTLS when we return a short write.

Instead, keep pushing until the OS will not take it.

The correct solution will be to use tls_tstream, but the client code
for this is not yet tested and needs the ldap client layer changed
to use it.

Andrew Bartlett

Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Wed Jul 18 11:23:55 CEST 2012 on sn-devel-104