Add new net command for text logging

Encapsulate the text in a payload, that also includes the
logging level and the time the event took place. The text
client will do as it always has done, but the gui client
can now do proper logging and knows if this is debug/info
or error messages.

No functional change in the GUI.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/log.c b/log.c
index af974f8..362ab23 100644
--- a/log.c
+++ b/log.c
@@ -60,7 +60,7 @@
 	va_end(args);
 
 	if (is_backend)
-		return fio_server_text_output(buffer, len);
+		return fio_server_text_output(FIO_LOG_INFO, buffer, len);
 	else if (log_syslog) {
 		syslog(LOG_INFO, "%s", buffer);
 		return len;
@@ -79,7 +79,7 @@
 	va_end(args);
 
 	if (is_backend)
-		return fio_server_text_output(buffer, len);
+		return fio_server_text_output(FIO_LOG_ERR, buffer, len);
 	else if (log_syslog) {
 		syslog(LOG_INFO, "%s", buffer);
 		return len;