bootstrap: make sure sfconf will be removed

Change-Id: I39e955303ecf891fb013ae9e4600d011f71ebea4
Use sshpass from EPEL

sshpass is included in the EPEL repository, so we can use it
directly without downloading it from Sourceforge.

Change-Id: Iefc3126a0ca94986c3bee4a06a6c0a897b496e9b