Don't use pq_putmessage in socket comm function

Hi,

Currently, socket_putmessage_noblock enlarges the output buffer and
then calls pq_putmessage to store the message in the buffer.

pq_putmessage is a macro redirecting to PqCommMethods->putmessage.
This is normally set to socket_putmessage, so
socket_putmessage_noblock calls socket_putmessage as desired.

However, if a custom PqCommMethods is defined, any call to
socket_putmessage_noblock will then loop to the custom putmessage.

This patch fixes the issue by directly using socket_putmessage in
socket_putmessage_noblock.

Regards,
Anthonin Bonnefoy