[autotest] Change "import utils" to use autotest_lib path

utils in rpm_control_system conflicts with autotest_lib.utils. To avoid any
confusion, replace "import utils" in rpm code with standard "common" way:

import common
from autotest_lib.site_utils.rpm_control_system import utils

BUG=None
TEST=unit test, load cl in destiny2 and start frontend and dispatcher.

Change-Id: I2e0bc01c1e9d763f818e1d2db1c7a5dd1d7834dd
Reviewed-on: https://chromium-review.googlesource.com/198413
Commit-Queue: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
diff --git a/site_utils/rpm_control_system/rpm_logging_config.py b/site_utils/rpm_control_system/rpm_logging_config.py
index cfa2f1b..c341ce3 100644
--- a/site_utils/rpm_control_system/rpm_logging_config.py
+++ b/site_utils/rpm_control_system/rpm_logging_config.py
@@ -9,6 +9,8 @@
 import time
 
 from config import rpm_config
+
+import common
 from autotest_lib.site_utils import log_socket_server
 
 LOGGING_FORMAT = rpm_config.get('GENERAL', 'logging_format')