MEDIUM: log: add a log level override value in struct session

This log level will be used in a further patch to change the log level
depending on the request or response.
diff --git a/src/peers.c b/src/peers.c
index 61fb938..998e61d 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1185,6 +1185,7 @@
 	 */
 
 	s->logs.logwait = 0;
+	s->logs.level = 0;
 	s->do_log = NULL;
 
 	/* default error reporting function, may be changed by analysers */