MXS-1267: Fix tee filter test results

The tests should no longer expect client session creation to fail if the
branch session creation is not successful.

The main session is kept alive so that a failure in the branch session
does not cause a failure of the main session. The main session can be
considered more important as it is what the client will use. If the branch
session fails, the failure will be logged so no information is lost.

Also added a missing configuration file and removed some extra-verbose
output in a test script.

maxscale-system-test/bug645_1.cpp

@@ -96,7 +96,6 @@ int main(int argc, char *argv[])
     Test->close_maxscale_connections();
 
     Test->check_log_err((char *) "Couldn't find suitable Master from 2 candidates", true);
-    Test->check_log_err((char *) "Creating client session for Tee filter failed. Terminating session.", true);
 
     int rval = Test->global_result;
     delete Test;