autotest: Drop spurious imports of lab_inventory

BUG=chromium:780892
TEST=None

Change-Id: I775d8c2f4133fc934b31a4bb6260b074eaf55947
Reviewed-on: https://chromium-review.googlesource.com/759717
Commit-Ready: Prathmesh Prabhu <[email protected]>
Tested-by: Prathmesh Prabhu <[email protected]>
Reviewed-by: Aviv Keshet <[email protected]>
diff --git a/scheduler/rdb_hosts.py b/scheduler/rdb_hosts.py
index 76fcd70..9ab9462 100644
--- a/scheduler/rdb_hosts.py
+++ b/scheduler/rdb_hosts.py
@@ -27,7 +27,6 @@
 from autotest_lib.frontend.afe import models as afe_models
 from autotest_lib.scheduler import rdb_requests
 from autotest_lib.scheduler import rdb_utils
-from autotest_lib.site_utils import lab_inventory
 from autotest_lib.site_utils import metadata_reporter
 from autotest_lib.site_utils.suite_scheduler import constants
 
@@ -269,7 +268,7 @@
         pool = ''
         if len(self.pools) == 1:
             pool = self.pools[0]
-        if pool in lab_inventory.MANAGED_POOLS:
+        if pool in constants.Pools.MANAGED_POOLS:
             pool = 'managed:' + pool
 
         metrics.String(self._HOST_POOL_METRIC,