vhost-user: Drop misleading EAGAIN checks in slave_read()

vhost-user: Drop misleading EAGAIN checks in slave_read()

slave_read() checks EAGAIN when reading or writing to the socket
fails. This gives the impression that the slave channel is in
non-blocking mode, which is certainly not the case with the current
code base. And the rest of the code isn't actually ready to cope
with non-blocking I/O.

Just drop the checks everywhere in this function for the sake of
clarity.

Signed-off-by: Greg Kurz <[email protected]>
Message-Id: <20210312092212[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>