Prevent CDR backends from unregistering while billing data is in flight

This patch makes it so that CDR backends cannot be unregistered while active
CDR records exist. This helps to prevent billing data from being lost during
restarts and shutdowns.

Review: https://reviewboard.asterisk.org/r/2880/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@402081 65c4cc65-6c06-0410-ace0-fbb531ad65f3

cdr/cdr_tds.c

@@ -443,6 +443,10 @@ failed:
 
 static int tds_unload_module(void)
 {
+	if (ast_cdr_unregister(name)) {
+		return -1;
+	}
+
 	if (settings) {
 		ast_mutex_lock(&tds_lock);
 		mssql_disconnect();
@@ -452,8 +456,6 @@ static int tds_unload_module(void)
 		ast_free(settings);
 	}
 
-	ast_cdr_unregister(name);
-
 	dbexit();
 
 	return 0;