tests: Initialize log system to fix crash, update test result

Use osmo_init_logging to initialize the log system to fix crashes
when we attempt to parse broken ASN1 messages.

Ignore stderr with parse errors, update the test result. make check
is now passing.
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 0e917f1..b33b04a 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -41,5 +41,5 @@
 AT_SETUP([ussd])
 AT_KEYWORDS([ussd])
 cat $abs_srcdir/ussd/ussd_test.ok > expout
-AT_CHECK([$abs_top_builddir/tests/ussd/ussd_test], [], [expout])
+AT_CHECK([$abs_top_builddir/tests/ussd/ussd_test], [], [expout], [ignore])
 AT_CLEANUP