IMPALA-6055: Fix hdfs encryption test far Hadoop 2.8+
IMPALA-6055: Fix hdfs encryption test far Hadoop 2.8+

Hadoop changed behavior regarding encrypted partitions and started
automatically provisioning .Trash directories in encrypted partitions.
This interplays poorly with the current test.

Change-Id: I30234aa50fea93f316e75beea2ced002dcea0c24
Reviewed-on: http://gerrit.cloudera.org:8080/8274
Tested-by: Impala Public Jenkins
Reviewed-by: Tim Armstrong <2f8e34250f03a653da3dc27f7ec203eafdde80fc@cloudera.com>

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala