iperf3: Fix iperf3cli.launch_sync() when configured to run more than 300 sec

process object always used timeout=300 while runnig wth launch_sync().
Let's allow replacing that value beforehand so that iperf3 can
pre-configure the process object and caller doesn't need to care about
calculating expected time.

Change-Id: I7f6c5078f648013515919aa35ebcdb3ef157b5e4
diff --git a/src/osmo_gsm_tester/core/process.py b/src/osmo_gsm_tester/core/process.py
index 8954674..1823a20 100644
--- a/src/osmo_gsm_tester/core/process.py
+++ b/src/osmo_gsm_tester/core/process.py
@@ -125,11 +125,14 @@
 
 class Process(log.Origin):
 
+    DEFAULT_WAIT_TIMEOUT = 300 # seconds
+
     def __init__(self, name, run_dir, popen_args, **popen_kwargs):
         super().__init__(log.C_RUN, name)
         self.process_obj = None
         self.result = None
         self.killed = None
+        self.default_wait_timeout = Process.DEFAULT_WAIT_TIMEOUT
         self.name_str = name
         self.run_dir = run_dir
         self.popen_args = popen_args
@@ -143,6 +146,10 @@
         env[key] = value
         self.popen_kwargs['env'] = env
 
+    def set_default_wait_timeout(self, timeout):
+        assert timeout
+        self.default_wait_timeout = timeout
+
     def make_output_log(self, name):
         '''
         create a non-existing log output file in run_dir to pipe stdout and
@@ -346,7 +353,9 @@
             self.poll()
         return self.result is not None
 
-    def wait(self, timeout=300):
+    def wait(self, timeout=None):
+        if timeout is None:
+            timeout = self.default_wait_timeout
         MainLoop.wait(self.terminated, timeout=timeout)
 
     def stdin_write(self, cmd):