Use a subdir of run_dir for each test

Processes created have the scope of the test, so we should store
everything in a per-suite_run/per-test directory, otherwise everything
is stored in the same trial run_dir directory and it's really messy.

Change-Id: I06be2dd21710e14c1337d13b1fe6c2f68f037957
diff --git a/src/osmo_gsm_tester/osmo_mgcpgw.py b/src/osmo_gsm_tester/osmo_mgcpgw.py
index b385274..db41dff 100644
--- a/src/osmo_gsm_tester/osmo_mgcpgw.py
+++ b/src/osmo_gsm_tester/osmo_mgcpgw.py
@@ -38,7 +38,7 @@
 
     def start(self):
         self.log('Starting osmo-mgcpgw')
-        self.run_dir = util.Dir(self.suite_run.trial.get_run_dir().new_dir(self.name()))
+        self.run_dir = util.Dir(self.suite_run.get_test_run_dir().new_dir(self.name()))
         self.configure()
         inst = util.Dir(os.path.abspath(self.suite_run.trial.get_inst('osmo-msc')))
         binary = inst.child('bin', 'osmo-bsc_mgcp')