system/fence-agents: Wrap README at 72 columns.

Signed-off-by: B. Watson <yalhcru@gmail.com>

system/fence-agents/README

@@ -1,9 +1,9 @@
 fence-agents (Cluster Fence Agents)
 
-Fence agents were developed as device "drivers" which are able to prevent
-computers from destroying data on shared storage. Their aim is to isolate
-a corrupted computer, using one of three methods: Power / Network /
-Configuration.
+Fence agents were developed as device "drivers" which are able to
+prevent computers from destroying data on shared storage. Their aim is
+to isolate a corrupted computer, using one of three methods: Power /
+Network / Configuration.
 
 You might also want to install cluster-glue, heartbeat, resource-agents,
 fence-agents.