Revert "Disable test broken by infra changes."

This reverts commit 4658efeb7831ec135f4642e3d4f3aeb7553e0c7e now the test infrastructure is fixed.

Bug: http://b/178980410
Change-Id: Ie263f8211c383eb0b2fe3d42852a535758d2898c
Test: none
diff --git a/test_adb.py b/test_adb.py
index 64278dc..a32d875 100755
--- a/test_adb.py
+++ b/test_adb.py
@@ -286,11 +286,9 @@
         os.name == "posix",
         "adb doesn't yet support IPv6 on Windows",
     )
-    def disabled_test_starts_on_ipv6_localhost(self):
+    def test_starts_on_ipv6_localhost(self):
         """
         Tests that the server can start up on ::1 and that it's accessible
-
-        Disabled due to b/178980410
         """
 
         server_port = find_open_port()