test-client.py: Close pipes and print logs on timeout failures

If we failed on process wait, we didn't close the pipes and no clear output
of what happened was exposed.

So use a finally stanza to close the pipes and print stdout and stderr
on failure.

clients/tests/test-client.py

@@ -425,15 +425,29 @@ class AsyncProcess():
 
         self.start()
 
+        error = False
+        try:
             Util.popen_wait(self._p, 2000)
-
+        except Exception as e:
-        (returncode, stdout, stderr) = (self._p.returncode, self._p.stdout.read(), self._p.stderr.read())
+            error = True
+            raise e
+        finally:
+            (returncode, stdout, stderr) = (self._p.returncode,
+                                            self._p.stdout.read(),
+                                            self._p.stderr.read())
 
             self._p.stdout.close()
             self._p.stderr.close()
             self._p = None
 
+            if error:
+                print(stdout)
+                print(stderr)
+
+        try:
             self._complete_cb(self, returncode, stdout, stderr)
+        except Exception as e:
+            raise e
 
 ###############################################################################