Fixed remote call in external HDFS configuration method

Before the change code was failing with exception. Probably
parentheses were not added during remote engine refactoring for
heat engine preparation.

Blueprint to create integration test: it-external-hdfs

Change-Id: If9aef3be0cc88133d6e20c9e3ffb1ef75e16443c
Closes-Bug: #1329079
Merge "Fixed remote call in external HDFS configuration method"