chore(test): fix flaky telemetry tests (#2815)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
This PR fixes flaky telemetry tests

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->
See https://github.com/meta-llama/llama-stack/pull/2814
## Test Plan
<!-- Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->

Signed-off-by: Mustafa Elbehery <melbeher@redhat.com>

llama_stack/providers/utils/telemetry/sqlite_trace_store.py

@@ -83,6 +83,7 @@ class SQLiteTraceStore(TraceStore):
             )
             SELECT DISTINCT trace_id, root_span_id, start_time, end_time
             FROM filtered_traces
+            WHERE root_span_id IS NOT NULL
             LIMIT {limit} OFFSET {offset}
         """
 
@@ -166,7 +167,11 @@ class SQLiteTraceStore(TraceStore):
                 return spans_by_id
 
     async def get_trace(self, trace_id: str) -> Trace:
-        query = "SELECT * FROM traces WHERE trace_id = ?"
+        query = """
+            SELECT *
+            FROM traces t
+            WHERE t.trace_id = ?
+        """
         async with aiosqlite.connect(self.conn_string) as conn:
             conn.row_factory = aiosqlite.Row
             async with conn.execute(query, (trace_id,)) as cursor: