GSM timers: User reasonable defaults; don't save if equal default

A number of the GSM timers (including T3109) had no reasonable
default values if not specified in the VTY / config file.  Together
with unconditional writing to the config file, this created
config files with a persistent setting for important timers as '0'.

To make things worse, many of our example cofig files suffered from the
same problem.

Let's avoid this from happening by
* having reasonable defaults if nothing specified in the config file
* conditionally savingg timers only if they differ from default
* reject any timer values that state zero during start-up (see previous
  commit)

Change-Id: Iaac0bfca423852b61d8b9eb1438157ef00d0d8c8
Closes: OS#2380
diff --git a/src/libbsc/net_init.c b/src/libbsc/net_init.c
index 4dfc258..9d54319 100644
--- a/src/libbsc/net_init.c
+++ b/src/libbsc/net_init.c
@@ -44,10 +44,17 @@
 	net->num_bts = 0;
 	net->reject_cause = GSM48_REJECT_ROAMING_NOT_ALLOWED;
 	net->T3101 = GSM_T3101_DEFAULT;
+	net->T3103 = GSM_T3103_DEFAULT;
 	net->T3105 = GSM_T3105_DEFAULT;
+	net->T3107 = GSM_T3107_DEFAULT;
+	net->T3109 = GSM_T3109_DEFAULT;
+	net->T3111 = GSM_T3111_DEFAULT;
 	net->T3113 = GSM_T3113_DEFAULT;
+	net->T3115 = GSM_T3115_DEFAULT;
+	net->T3117 = GSM_T3117_DEFAULT;
+	net->T3119 = GSM_T3119_DEFAULT;
 	net->T3122 = GSM_T3122_DEFAULT;
-	/* FIXME: initialize all other timers! */
+	net->T3141 = GSM_T3141_DEFAULT;
 
 	/* default set of handover parameters */
 	net->handover.win_rxlev_avg = 10;