Fixing pdsh issue.

Added single quotes to each pdsh command so that it will be executed
correctly.

Edit: Removed single quotes around commands with variables.

Edit 2: Changes made from comments by reviewers.

Edit 3: dcs_installer change.

Edit 4: traf_cloudera_uninstaller change.

Change-Id: I2c0b81d8780b8c0c273217e0b0c88db6fe4f60df