test: netns: Clean up lingering namespaces on test exit

This gets rid of annoying "Address already in use" errors when running
tests repeatedly from a test-sh.

test/infamy/netns.py

@@ -41,6 +41,11 @@ class IsolatedMacVlans:
 
     """
 
+    Instances = []
+    def Cleanup():
+        for ns in list(IsolatedMacVlans.Instances):
+            ns.stop()
+
     def __init__(self, ifmap, lo=True):
         self.sleeper = None
         self.ifmap, self.lo = ifmap, lo
@@ -76,11 +81,13 @@ def start(self):
                 self.__exit__(None, None, None)
                 raise e
 
+        self.Instances.append(self)
         return self
 
     def stop(self):
         self.sleeper.kill()
         self.sleeper.wait()
+        self.Instances.remove(self)
         time.sleep(0.5)
 
     def __enter__(self):

test/infamy/tap.py

@@ -4,6 +4,8 @@
 import sys
 import traceback
 
+import infamy.netns
+
 class Test:
     def __init__(self, output=sys.stdout):
         self.out = output
@@ -24,6 +26,8 @@ def __exit__(self, _, e, __):
         self.out.write(f"# Exiting ({now})\n")
         self.out.flush()
 
+        infamy.netns.IsolatedMacVlans.Cleanup()
+
         if not e:
             self._not_ok("Missing explicit test result\n")
         else: