tests: fix timeout adjustement in delaypush.py

Doing integer arithmetic with string is bound to fail.

tests/test-push-race.t

@@ -50,6 +50,10 b' A set of extension and shell functions e'
   >         limit = 100
   >         test_default_timeout = os.environ.get('HGTEST_TIMEOUT_DEFAULT')
   >         test_timeout = os.environ.get('HGTEST_TIMEOUT')
+  >         if test_default_timeout is not None:
+  >            test_default_timeout = int(test_default_timeout)
+  >         if test_timeout is not None:
+  >            test_timeout = int(test_timeout)
   >         if (
   >             test_default_timeout is not None
   >             and test_timeout is not None