Fix intermittent test failure in tests/test_message_meta.py (nv-morph…

…eus#772)

We had two tests that set values on row 3, however we now randomly duplicate the index, causing a situation where 3 might not exist in the index.

Authors:
  - David Gardner (https://github.com/dagardner-nv)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: nv-morpheus#772

tests/test_message_meta.py

@@ -105,9 +105,9 @@ def test_mutable_dataframe(df: cudf.DataFrame):
     meta = MessageMeta(df)
 
     with meta.mutable_dataframe() as df:
-        df['v2'][3] = 47
+        df['v2'].iloc[3] = 47
 
-    assert meta.copy_dataframe()['v2'][3] == 47
+    assert meta.copy_dataframe()['v2'].iloc[3] == 47
 
 
 def test_using_ctx_outside_with_block(df: cudf.DataFrame):
@@ -136,5 +136,6 @@ def test_copy_dataframe(df: cudf.DataFrame):
     assert copied_df is not df, "But should be different instances"
 
     # Try setting a single value on the copy
-    meta.copy_dataframe()['v2'][3] = 47
+    cdf = meta.copy_dataframe()
+    cdf['v2'].iloc[3] = 47
     assert assert_df_equal(meta.copy_dataframe(), df), "Should be identical"