[Spark] Fix Utils.isTesting calls to use Delta implementation

[felipepessoto]

Which Delta project/connector is this regarding?

• Spark
• Standalone
• Flink
• Kernel
• Other (fill in here)

Description

Some classes were using the org.apache.spark.util.Utils instead of the org.apache.spark.sql.delta.util.Utils

The Spark implementation uses the SPARK_TESTING environment variable, while the Delta implementation uses the DELTA_TESTING key.

Spark:
https://github.com/apache/spark/blob/51fb84a54982719209c19136b1d72d2ef44726ee/core/src/main/scala/org/apache/spark/util/Utils.scala#L1878

Delta:

delta/spark/src/main/scala/org/apache/spark/sql/delta/util/Utils.scala

Line 58 in 221d95c

System.getenv("DELTA_TESTING") != null

It means the unit tests are currently running non test code path, because we only set the DELTA_TESTING:

delta/build.sbt

Line 466 in 221d95c

Test / envVars += ("DELTA_TESTING", "1"),

delta/run-tests.py

Line 93 in 221d95c

run_cmd(["python3", python_test_script], env={'DELTA_TESTING': '1'}, stream_output=True)

How was this patch tested?

Unit tests

Does this PR introduce any user-facing changes?

No