core: Adds task description for SshSoftFencingCommand

Adds task description for SshSoftFencingCommand.

Change-Id: Iaa947dde1d93c7e8c96e111b02a55a2a179d3f9b
Bug-Url: https://bugzilla.redhat.com/988305
Signed-off-by: Martin Perina <mperina@redhat.com>