Revert OS version change.

Author: r12f

tests/common/telemetry/base.py

@@ -147,7 +147,7 @@ def _detect_test_context(self, request=None, tbinfo=None) -> Dict[str, str]:
         if not context.get(METRIC_LABEL_TEST_TESTBED):
             context[METRIC_LABEL_TEST_TESTBED] = os.environ.get(ENV_SONIC_MGMT_TESTBED_NAME, 'unknown')
 
-        context[METRIC_LABEL_TEST_OS_VERSION] = duthost.os_version
+        context[METRIC_LABEL_TEST_OS_VERSION] = os.environ.get(ENV_SONIC_MGMT_BUILD_VERSION, 'unknown')
         context[METRIC_LABEL_TEST_JOB_ID] = os.environ.get(ENV_SONIC_MGMT_JOB_ID, 'unknown')
 
         return context