fencing: stop using a deprecated command

Recently, fence-agents stopped supporting the "option" alias for its
"action" STDIN command.

https://lists.fedorahosted.org/pipermail/cluster-commits/2013-February/003090.html

Let us conform to the new option name. The "action" name has been long
supported by el6 and f19's fence-agents, so it can be safely used.

Thanks to John Taylor for reporting the issue.

Bug-Url: https://bugzilla.redhat.com/1063472
Change-Id: Ia0e167e493412f95eda2325e0b028eb7c29c18bc
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/24303
Reviewed-by: Eli Mesika <emesika@redhat.com>
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>