Try fix behaviour when network is not available at bootup

--- ./ntp_sources.c.orig
+++ ./ntp_sources.c
@@ -109,7 +109,7 @@
 
 #define RESOLVE_INTERVAL_UNIT 7
 #define MIN_RESOLVE_INTERVAL 2
-#define MAX_RESOLVE_INTERVAL 9
+#define MAX_RESOLVE_INTERVAL 6
 #define MAX_REPLACEMENT_INTERVAL 9
 
 static struct UnresolvedSource *unresolved_sources = NULL;