CDH-27688: Isilon: fix custom_cluster/test_insert_inherit_permission.py
CDH-27688: Isilon: fix custom_cluster/test_insert_inherit_permission.py

Workaround innocuous Isilon HDFS permission differences:

1) x permission is needed to rm a directory on Isilon (which is
   arguably more correct).  Workaround this by using 744 rather than
   644 permissions.
2) Isilon follows HDFS v4 convention for permission inheritance which
   means first level child gets the parent's permissions.  Workaround by
   skipping this check on Isilon, but add a check for the grandchild.

Change-Id: I5b651214dd3e0c8f72017fda8f9705d72b663dae
Reviewed-on: http://gerrit.cloudera.org:8080/429
Reviewed-by: Dan Hecht <20ebd99959f0f6e5dcb0fc319b4d8ef53a16b5fb@cloudera.com>
Tested-by: Internal Jenkins
Reviewed-on: http://gerrit.cloudera.org:8080/438
Tested-by: Ishaan Joshi <d1d1e60202ec9f2503deb1b724986485a125d802@cloudera.com>

scalingdata/Impala,scalingdata/Impala,scalingdata/Impala,scalingdata/Impala,scalingdata/Impala,scalingdata/Impala