sgsn: osmo-*.cfg: tune logging configuration

Change-Id: I2f2cc69a481709e862d569b0298561b61506dfa7
diff --git a/sgsn/osmo-sgsn.cfg b/sgsn/osmo-sgsn.cfg
index b446f87..4a5f236 100644
--- a/sgsn/osmo-sgsn.cfg
+++ b/sgsn/osmo-sgsn.cfg
@@ -8,12 +8,12 @@
 !
 log stderr
  logging filter all 1
- logging color 1
- logging print category 1
- logging print category-hex 0
- logging timestamp 1
  logging print extended-timestamp 1
- logging print file 1
+ logging print file basename last
+ logging print category-hex 0
+ logging print category 1
+ logging print level 1
+ logging color 1
  logging level mm debug
  logging level pag notice
  logging level meas notice