logging/vty: fix vty_read_file(): do not write warnings to stdin

Setting vty->fd to 0 is a bad idea, which may cause the process
to write() warnings to its own _stdin_ (yes, it's possible).
For example, when a configuration file contains deprecated
logging commands. Let's use stderr by default.

Change-Id: Icdeaea67a06da3a2f07b252e455629559ecc1829
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 5865140..c231b96 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -199,10 +199,7 @@
 AT_KEYWORDS([vty])
 cat $abs_srcdir/vty/vty_test.ok > expout
 cp $abs_srcdir/vty/*.cfg .
-# FIXME: calling vty_out() during initialization of the VTY interface would cause
-# the process write to its own *stdin*! This breaks the output of 'make check'.
-# Let's work this around untill the bug in libosmovty is fixed.
-AT_CHECK([$abs_top_builddir/tests/vty/vty_test 0>/dev/null], [0], [expout], [ignore])
+AT_CHECK([$abs_top_builddir/tests/vty/vty_test], [0], [expout], [ignore])
 AT_CLEANUP
 
 AT_SETUP([gprs-bssgp])