[SPARK-25930][K8S] Fix scala string detection in k8s tests

## What changes were proposed in this pull request?

- Issue is described in detail in [SPARK-25930](https://issues.apache.org/jira/browse/SPARK-25930). Since we rely on the std output, pick always the last line which contains the wanted value. Although minor, current implementation breaks tests.

## How was this patch tested?
manually. rm -rf ~/.m2 and then run the tests.

Closes apache#22931 from skonto/fix_scala_detection.

Authored-by: Stavros Kontopoulos <[email protected]>
Signed-off-by: Sean Owen <[email protected]>
(cherry picked from commit 1fb3759)
Signed-off-by: Sean Owen <[email protected]>

Author: Stavros Kontopoulos

resource-managers/kubernetes/integration-tests/dev/dev-run-integration-tests.sh

@@ -28,7 +28,12 @@ NAMESPACE=
 SERVICE_ACCOUNT=
 INCLUDE_TAGS="k8s"
 EXCLUDE_TAGS=
-SCALA_VERSION="$($TEST_ROOT_DIR/build/mvn org.apache.maven.plugins:maven-help-plugin:2.1.1:evaluate -Dexpression=scala.binary.version | grep -v '\[' )"
+MVN="$TEST_ROOT_DIR/build/mvn"
+
+SCALA_VERSION=$("$MVN" help:evaluate -Dexpression=scala.binary.version 2>/dev/null\
+    | grep -v "INFO"\
+    | grep -v "WARNING"\
+    | tail -n 1)
 
 # Parse arguments
 while (( "$#" )); do