Logger: Use libosmocore logging system

We still need an intermediate class Logger due to osmo-trx being
multi-threaded and requiring to have a lock to use libosmocore, which is
not thread safe.

Change-Id: I30baac89f53e927f8699d0586b43cccf88ecd493
diff --git a/tests/CommonLibs/LogTest.err b/tests/CommonLibs/LogTest.err
index 718ff40..153e850 100644
--- a/tests/CommonLibs/LogTest.err
+++ b/tests/CommonLibs/LogTest.err
@@ -1,24 +1,3 @@
-EMERG  testing the logger.
-ALERT  testing the logger.
-CRIT  testing the logger.
-ERR  testing the logger.
-ALERT 0
-ALERT 1
-ALERT 2
-ALERT 3
-ALERT 4
-ALERT 5
-ALERT 6
-ALERT 7
-ALERT 8
-ALERT 9
-ALERT 10
-ALERT 11
-ALERT 12
-ALERT 13
-ALERT 14
-ALERT 15
-ALERT 16
-ALERT 17
-ALERT 18
-ALERT 19
+FATAL testing the logger.
+ERROR testing the logger.
+NOTICE testing the logger.