mtest: store the environment in the TestRun
The test_env was lost from the TestRun object in commit
("mtest: create TestRun object early on").  Fix
things.
@@ -746,7 +746,7 @@ class TestRun:
self.stdo = None # type: T.Optional[str]
self.stde = None # type: T.Optional[str]
self.cmd = None # type: T.Optional[T.List[str]]
- self.env = dict() # type: T.Dict[str, str]
+ self.env = test_env # type: T.Dict[str, str]
self.should_fail = test.should_fail
self.project = test.project_name
self.junit = None # type: T.Optional[et.ElementTree]
