osmo-hlr: allow configuring db path from cfg file

So far, the cmdline argument was the only way to set a database config file.
Add a similar config to VTY as 'hlr' / 'database'. The cmdline arg is stronger
than the 'database' cfg item. DB is not reloaded from VTY command.

Change-Id: I87b8673324e1e6225afb758fb4963ff3279ea3d8
diff --git a/tests/test_nodes.vty b/tests/test_nodes.vty
index d90fa70..a4e53db 100644
--- a/tests/test_nodes.vty
+++ b/tests/test_nodes.vty
@@ -75,6 +75,7 @@
   exit
   end
   gsup
+  database PATH
   euse NAME
   no euse NAME
   ussd route prefix PREFIX internal (own-msisdn|own-imsi)
@@ -124,6 +125,7 @@
 ...
 hlr
  store-imei
+ database hlr_vty_test.db
  gsup
   bind ip 127.0.0.1
  ussd route prefix *#100# internal own-msisdn