SocketOperation: return the number of chars written
SocketOperation: return the number of chars written

Callers deal with strings, so it's the number of chars we should return
rather than the number of bytes.

Note that this is only relevant if we pass non-ascii information over
HTTP.

Signed-off-by: Apollon Oikonomopoulos <ed81ed0a45ccd5c8869bda52e38353a6299ee39e@dmesg.gr>

ganeti/ganeti,ganeti/ganeti,ganeti/ganeti