make it optional where the hlr database is stored

Add --database to define where the database is stored. The default
was changed to not store the file in /tmp anymore.
diff --git a/src/db_test.c b/src/db_test.c
index 0367ce2..760d7ab 100644
--- a/src/db_test.c
+++ b/src/db_test.c
@@ -25,7 +25,7 @@
 
 int main() {
 
-	if (db_init()) {
+	if (db_init("hlr.sqlite3")) {
 		printf("DB: Failed to init database. Please check the option settings.\n");
 		return 1;
 	}